bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inhibition of kinin breakdown prolongs retention and action of bradykinin in a myocardial B2 receptor compartment
Authors: Dendorfer Andreas , Folkers Verena , Klinger Matthias , Wolfrum Sebastian , Dominiak Peter 
Published: February 2003

The high efficacy of ACE inhibitors to potentiate the actions of kinins might be explained by a hypothetical compartment in which B2‐receptors are colocalized with kinin degrading enzymes. To demonstrate the functional consequence of such a compartment we compared the myocardial uptake and the persistence of action of bradykinin under the influence of kininase inhibitors.
Bradykinin‐induced vasodilation and uptake of tritiated bradykinin were studied in perfused rat hearts during inhibition of ACE and aminopeptidase P. B2‐receptors were localized by immuno‐gold labelling and electron‐microscopy.
The EC50 of bradykinin‐induced vasodilation (5.1±0.8 nM) was shifted to 14 fold lower concentrations during inhibition of both kininases. The maximum persistence of vasodilation after termination of bradykinin application (half‐life 112±20 s) was increased by kininase inhibitors to 398±130 s. This prolongation was reversed when B2‐receptors were blocked simultaneously with the termination of bradykinin infusion.
Tritiated bradykinin (perfused for 1 min) was partially (1.7±0.24%) retained by the myocardium and consecutively released with a half‐life of 70±9 s. Kinin uptake was increased during kininase inhibition (7.7±2.6%), and was normalized by HOE 140 (2.0±0.34%), or when a tritiated B2‐receptor antagonist (NPC 17731) was used as label.
B2‐receptors were localized in plasmalemmal and cytosolic vesicles of capillary endothelium.
Bradykinin is locally incorporated and can associate with B2‐receptors repeatedly when kinin breakdown is inhibited. This is the kinetic and functional consequence of a colocalization of kininases and B2‐receptors in a compartment constituted by endothelial membrane vesicles.

British Journal of Pharmacology (2003) 138, 310–316. doi:10.1038/sj.bjp.0705036
Attenuation of the P2Y receptor‐mediated control of neuronal Ca2+ channels in PC12 cells by antithrombotic drugs
Authors: Kubista Helmut , Lechner Stefan G , Wolf Angelika M , Boehm Stefan 
Published: February 2003

In PC12 cells, adenine nucleotides inhibit voltage‐activated Ca2+ currents and adenylyl cyclase activity, and the latter effect was reported to involve P2Y12 receptors. To investigate whether these two effects are mediated by one P2Y receptor subtype, we used the antithrombotic agents 2‐methylthio‐AMP (2‐MeSAMP) and N6‐(2‐methyl‐thioethyl)‐2‐(3,3,3‐trifluoropropylthio)‐β,γ‐dichloromethylene‐ATP (AR‐C69931MX).
ADP reduced A2A receptor‐dependent cyclic AMP synthesis with half maximal effects at 0.1–0.17 μM. In the presence of 30 μM 2‐MeSAMP or 100 nM AR‐C69931MX, concentration response curves were shifted to the right by factors of 39 and 30, indicative of pA2 values of 6.1 and 8.5, respectively.
The inhibition of Ca2+ currents by ADP was attenuated by 10–1000 nM AR‐C69931MX and by 3–300 μM 2‐MeSAMP. ADP reinhibited Ca2+ currents after removal of 2‐MeSAMP within less than 15 s, but required 2 min to do so after removal of AR‐C69931MX.
ADP inhibited Ca2+ currents with half maximal effects at 5–20 μM. AR‐C69931MX (10–100 nM) displaced concentration response curves to the right, and the resulting Schild plot showed a slope of 1.09 and an estimated pKB value of 8.7. Similarly, 10–100 μM 2‐MeSAMP also caused rightward shifts resulting in a Schild plot with a slope of 0.95 and an estimated pKB of 5.4.
The inhibition of Ca2+ currents by 2‐methylthio‐ADP and ADPβS was also antagonized by AR‐C69931MX, which (at 30 nM) caused a rightward shift of the concentration response curve for ADPβS by a factor of 3.8, indicative of a pA2 value of 8.1.
These results show that antithrombotic drugs antagonize the inhibition of neuronal Ca2+ channels by adenine nucleotides, which suggests that this effect is mediated by P2Y12 receptors.

British Journal of Pharmacology (2003) 138, 343–350. doi:10.1038/sj.bjp.0705037
Tacrolimus and sirolimus decrease oxidative phosphorylation of isolated rat kidney mitochondria
Authors: Simon Nicolas , Morin Christophe , Urien Saïk , Tillement Jean‐Paul , Bruguerolle Bernard 
Published: February 2003

Tacrolimus and sirolimus are potent immunosuppressors used in transplantation. Tacrolimus has been suspected to alter mitochondrial respiration of different tissues but sirolimus has not been evaluated.
We evaluated the in vitro effect of tacrolimus and sirolimus on oxidative phosphorylation of isolated rat kidney mitochondria.
Oxygen consumption was measured with a Clark‐type electrode. Tacrolimus and sirolimus increased the resting rate (state 4) and had no significant effect on ADP‐stimulated respiration (state 3). The decrease of respiratory control ratio was concentration‐dependent with a biphasic curve for tacrolimus. The EC50s were 3.4×10−11 M and 2.3×10−8 M for tacrolimus and 4.4×10−10 M for sirolimus. The maximal inhibition was 20 and 14% for tacrolimus and sirolimus, respectively.
Tacrolimus and sirolimus had an uncoupling effect on oxidative phosphorylation related to a decrease of the inner membrane fluidity. At the opposite of cyclosporin A, no effect on swelling or Ca2+ fluxes was observed.
All events occurred at therapeutic concentrations and then could appear during long‐term treatment. Cellular consequences such as chronic nephrotoxicity with tacrolimus are suggested. The risk of cyclosporin A nephrotoxicity potentiation by sirolimus is discussed.

British Journal of Pharmacology (2003) 138, 369–376. doi:10.1038/sj.bjp.0705038
Bradykinin increases intracellular calcium levels in rat testis peritubular cells via the B2 receptor subtype
Authors: Wennemuth Gunther , Blöcher Sonja , Schill Wolf‐Bernhard , Aumüller Gerhard , Monsees Thomas K 
Published: February 2003

RT–PCR and Western blots were used to detect bradykinin B2 receptors in testis and isolated peritubular cells of pre‐pubertal rats. RT–PCR demonstrated expression of a single transcript, whereas Western blots showed up to three specific bands that were in accordance with the described native, glycosylated and dimeric form of B2 receptor proteins, respectively.
Fura‐2‐loaded peritubular cells responded with an instantaneous, linear and transient rise in [Ca2+]i after adding bradykinin. Stimulation of cells with bradykinin concentrations between 1 μM and 1 pM showed a dose dependent increase of [Ca2+]i. The calcium response to bradykinin was diminished after stimulation of peritubular cells in calcium‐free buffer. After blocking the SERCA‐pumps by thapsigargin and subsequent stimulation with bradykinin, no rise of [Ca2+]i was appreciated.
Multiple stimulation of a single peritubular cell by local perfusion with a brief addition of BK (10 nM) resulted in a fast and immediate response. However, the second and third stimuli had slower rise rates and diminished [Ca2+]i peaks, showing desensitization of the kinin receptor.
Addition of the bradykinin B1 receptor agonist [des‐Arg9]‐bradykinin (100 nM) to Fura‐2‐loaded peritubular cells did not change the [Ca2+]i. However, the B2 receptor antagonist HOE 140 (100 nM) strongly inhibited the bradykinin‐induced calcium response.
We conclude that the bradykinin‐induced increase in [Ca2+]i, in testicular peritubular cells is mediated by the stimulation of kinin receptors of the B2 subtype.

British Journal of Pharmacology (2003) 138, 351–358. doi:10.1038/sj.bjp.0705039
The role of the 8‐18 helix of CGRP8‐37 in mediating high affinity binding to CGRP receptors; coulombic and steric interactions
Authors: Howitt Stephen G , Kilk Kalle , Wang Yang , Smith David M , Langel Ulo , Poyner David R 
Published: February 2003

The role of individual residues in the 8‐18 helix of CGRP8‐37 in promoting high‐affinity binding to CGRP1 receptors expressed on rat L6 and human SK‐N‐MC cells has been examined. The relative potencies of various derivatives were estimated from their ability to inhibit the human αCGRP‐mediated increase in cyclic AMP production and the binding of [125I]‐human αCGRP.
Arg11 and Arg18 were replaced by serines to give [Ser11,18]CGRP8‐37. These bound with pKi values <6 to SK‐N‐MC cells and had apparent pA2 values of 5.81±0.04 and 5.31±0.11 on SK‐N‐MC and L6 cells. CGRP8‐37 had a pKi of 8.22 on SK‐N‐MC cells and pKb values on the above cell lines of 8.95±0.04 and 8.76±0.04.
The arginines were replaced with glutamic acid residues. [Glu11]CGRP8‐37 had a pKb of 7.14±0.14 on SK‐N‐MC cells (pKi=7.05±0.05) and 6.99±0.08 on L6 cells. [Glu18]CGRP8‐37 had a pKb of 7.10±0.0.08 on SK‐N‐MC cells (pKi=6.91±0.23) and 7.12±0.09 on L6 cells.
Leu12, Leu15 and Leu16 were replaced by benzoyl‐phenylalanine (bpa) residues. On SK‐N‐MC cells, the apparent pA2 values of [bpa12]‐, [bpa15]‐ and [bpa16]CGRP8‐37 were respectively 7.43±0.23, 8.34±0.11 and 5.66±0.16 (pKi values of 7.14±0.17, 7.66±0.21 and <6): on L6 cells they were 7.96±0.36, 8.28±0.21 and 6.09±0.04 (all n=3).
It is concluded that the Arg11 and Arg18 are involved in specific electrostatic interactions with other residues, either on the CGRP1 receptors or elsewhere on CGRP8‐37. Leu16 is in a conformationally restricted site when CGRP8‐37 binds to CGRP1 receptors, unlike Leu12 and Leu15.

British Journal of Pharmacology (2003) 138, 325–332. doi:10.1038/sj.bjp.0705040
Coupling of the nucleotide P2Y4 receptor to neuronal ion channels
Authors: Filippov Alexander K , Simon Joseph , Barnard Eric A , Brown David A 
Published: February 2003

G protein‐linked P2Y nucleotide receptors are known commonly to stimulate the phosphoinositide signalling pathway. However, we have previously demonstrated that the cloned P2Y2, P2Y6 and P2Y1 receptors couple to neuronal N‐type Ca2+ channels and to M‐type K+ channels. Here we investigate the coupling of recombinant, neuronally expressed rat‐ and human P2Y4 receptors (rP2Y4, hP2Y4) to those channels.
Rat sympathetic neurones were nuclear‐injected with a P2Y4 cDNA plasmid. A subsequent activation of rP2Y4 or hP2Y4 by UTP (100 μM) in whole‐cell (ruptured‐patch) mode produced only about 12% inhibition of the N‐type Ca2+ current (ICa(N)). Surprisingly, in perforated patch mode, UTP produced much more inhibition of ICa(N) (maximally 51%), with an IC50 value of 273 nM. This inhibition was voltage‐dependent and was blocked by co‐expression of the βγ‐binding transducin Gα‐subunit. Pertussis toxin (PTX) pretreatment also suppressed ICa(N) inhibition.
UTP inhibited the M‐current, recorded in perforated patch mode, by (maximally) 52%, with IC50 values of 21 nM for rP2Y4 and 28 nM for hP2Y4. This inhibition was not affected by PTX pretreatment.
With rP2Y4, ATP inhibited the M‐current (IC50 524 nM, 26 times weaker than UTP), whereas ATP had no agonist activity at hP2Y4. This suggests a difference in agonist binding site between rP2Y4 and hP2Y4.
We conclude that, in contrast to other nucleotide receptors studied, the P2Y4 receptor couples much more effectively to M‐type K+ channels than to Ca2+ channels. Coupling to the Ca2+ channels involves the βγ‐subunits of Gi/o‐proteins and requires a diffusible intracellular component that is lost in ruptured‐patch recording.

British Journal of Pharmacology (2003) 138, 400–406. doi:10.1038/sj.bjp.0705043
Isolation and pharmacological characterization of a phospholipase A2 myotoxin from the venom of the Irian Jayan death adder (Acanthophis rugosus)
Authors: Wickramaratna Janith C , Fry Bryan G , Aguilar Marie‐Isabel , Kini R Manjunatha , Hodgson Wayne C 
Published: February 2003

It has long been thought that death adder venoms are devoid of myotoxic activity based on studies done on Acanthophis antarcticus (Common death adder) venom. However, a recent clinical study reported rhabdomyolysis in patients following death adder envenomations, in Papua New Guinea, by a species thought to be different to A. antarcticus. Consequently, the present study examined A. rugosus (Irian Jayan death adder) venom for myotoxicity, and isolated the first myotoxin (acanmyotoxin‐1) from a death adder venom.
A. rugosus (10–50 μg ml−1) and acanmyotoxin‐1 (MW 13811; 0.1–1 μM) were screened for myotoxicity using the chick directly (0.1 Hz, 2 ms, supramaximal V) stimulated biventer cervicis nerve‐muscle (CBCNM) preparation. A significant contracture of skeletal muscle and/or inhibition of direct twitches were considered signs of myotoxicity. This was confirmed by histological examination.
High phospholipase A2 (PLA2) activity was detected in both A. rugosus venom (140.2±10.4 μmol min−1 mg−1; n=6) and acanmyotoxin‐1 (153.4±11 μmol min−1 mg−1; n=6). Both A. rugosus venom (10–50 μg ml−1) and acanmyotoxin‐1 (0.1–1 μM) caused dose‐dependent inhibition of direct twitches and increase in baseline tension (n=4–6). In addition, dose‐dependent morphological changes in skeletal muscle were observed.
Prior incubation (10 min) of CSL death adder antivenom (5 units ml−1; n=4) or inactivation of PLA2 activity with 4‐bromophenacyl bromide (1.8 mM; n=4) prevented the myotoxicity caused by acanmyotoxin‐1 (1 μM).
Acanmyotoxin‐1 (0.1 μM; n=4) displayed no significant neurotoxicity when it was examined using the indirectly (0.1 Hz, 0.2 ms, supramaximal V) stimulated CBCNM preparation.
In conclusion, clinicians may need to be mindful of possible myotoxicity following death adder envenomation in Irian Jaya.

British Journal of Pharmacology (2003) 138, 333–342. doi:10.1038/sj.bjp.0705046
Pharmacological characterization of a 1,4‐dihydropyridine analogue, 9‐(3,4‐dichlorophenyl)‐3,3,6,6‐tetramethyl‐3,4,6,7,9,10‐hexahydro‐1,8(2H,5H)‐acridinedione (A‐184209) as a novel KATP channel inhibitor
Authors: Gopalakrishnan Murali , Miller Thomas R , Buckner Steven A , Milicic Ivan , Molinari Eduardo J , Whiteaker Kristi L , Davis‐Taber Rachel , Scott Victoria E , Cassidy Christopher , Sullivan James P , Carroll William A 
Published: February 2003

This study reports on the identification and characterization of a 1,4‐dihydropyridine analogue, 9‐(3,4‐dichlorophenyl)‐3,3,6,6‐tetramethyl‐3,4,6,7,9,10‐hexahydro‐1,8(2H,5H)‐acridinedione (A‐184209) as a novel inhibitor of ATP‐sensitive K+ channels.
A‐184209 inhibited membrane potential changes evoked by the prototypical cyanoguanidine ATP‐sensitive K+ channel opener (KCO) P1075 in both vascular (A10) and urinary bladder smooth muscle cells with IC50 values of 1.44 and 2.24 μM respectively.
P1075‐evoked relaxation of 25 mM K+ stimulated aortic strips was inhibited by A‐184209 in an apparently competitive fashion with a pA2 value of 6.34.
The potencies of A‐184209 to inhibit P1075‐evoked decreases in membrane potential responses in cardiac myocytes (IC50=0.53 μM) and to inhibit 2‐deoxyglucose‐evoked cation efflux pancreatic RINm5F cells (IC50=0.52 μM) were comparable to the values for inhibition of smooth muscle KATP channels.
On the other hand, a structural analogue of A‐184209 that lacked the gem‐dimethyl substituent, 9‐(3,4‐dichlorophenyl)‐3,4,6,7,9,10‐hexahydro‐1,8(2H,5H)‐acridinedione (A‐184208), was found to be a KATP channel opener, evoking membrane potential responses in A10 smooth muscle cells (EC50=385 nM) and relaxing aortic smooth muscle strips (IC50=101 nM) in a glyburide‐sensitive manner.
Radioligand binding studies demonstrated that A‐184209 displaced SUR1 binding defined by [3H]glyburide binding to RINm5F cell membranes with a Ki value of 0.11 μM whereas A‐184208 was ineffective. On the other hand, both A‐184209 (Ki=1.34 μM) and A‐184208 (Ki=1.14 μM) displaced binding of the KCO radioligand, [125I]A‐312110 in guinea‐pig bladder membranes with similar affinities.
These studies demonstrate that A‐184209 is a novel and structurally distinct compound that inhibits KATP channels in smooth muscle with potencies comparable to glyburide. The structural overlap between DHP openers and blockers, together with their differential interaction with ligand binding sites, support the notion that both openers and blockers bind to similar or very closely coupled sites on the sulfonylurea receptor and that subtle changes in the pharmacophore itself could switch functional properties from KATP channel activation to inhibition.

British Journal of Pharmacology (2003) 138, 393–399. doi:10.1038/sj.bjp.0705048
Alprostadil suppresses angiogenesis in vitro and in vivo in the murine Matrigel plug assay
Authors: Cattaneo Maria Grazia , Pola Sandra , Dehò Valeria , Sanguini Anna Maria , Vicentini Lucia Maria 
Published: February 2003

Prostaglandin E1 (PGE1, alprostadil) is used as a vasodilator for the treatment of peripheral vascular diseases.
Previous reports suggested a pro‐angiogenic effect for PGE1.
We studied the in vitro and in vivo effect of PGE1, complexed with α‐cyclodextrin, on the angiogenic process. Contrary to what was expected, we found that, in human umbilical vein endothelial cells (HUVECs), PGE1 inhibited proliferation, migration and capillary‐like structure formation in Matrigel.
By RT–PCR studies, the expression of the EP2 and EP3 subtypes of the PG receptor was detected in HUVECs.
PGE1 alone stimulated adenylate cyclase activity at micromolar concentrations, while at nanomolar concentrations potentiated the forskolin‐induced cAMP accumulation.
8‐Bromoadenosine‐3′:5′‐cyclic monophosphate (Br‐cAMP) mimicked the inhibitory effect of PGE1 on endothelial cell growth, motility and tube formation.
Sulprostone, an agonist at the EP3 subtype of PG receptors, mimicked the in vitro anti‐angiogenic effects of PGE1, while butaprost, an EP2 receptor agonist, had no effect.
Finally, in the plug assay model of angiogenesis in mice, PGE1 showed a strong inhibitory effect on Matrigel neovascularization.
Thus, PGE1 possesses strong anti‐angiogenic activity in vitro and in vivo.

British Journal of Pharmacology (2003) 138, 377–385. doi:10.1038/sj.bjp.0705051
The Rho‐kinase inhibitor Y‐27632 and the soluble guanylyl cyclase activator BAY41‐2272 relax rabbit vaginal wall and clitoral corpus cavernosum
Authors: Cellek Selim 
Published: February 2003

The effects of Y‐27632, a Rho‐kinase inhibitor and BAY41‐2272, a soluble guanylyl cyclase activator, on the tone and nitrergic responses of rabbit vaginal wall and clitoral corpus cavernosum were investigated. Y‐27632 and BAY41‐2272 (10 nM–10 μM) elicited concentration‐dependent relaxation of phenylephrine‐induced tone in both tissues. IC50 values of Y‐27632 for vaginal and clitoral tissues were 370±30 nM, and 467±14 nM, respectively. BAY41‐2272 had IC50 values of 478±54 nM and 304±38 nM respectively. The effect of the Y‐27632 on the tissue tone was not affected by an inhibitor of nitric oxide synthase (L‐NAME; 500 μM). However, L‐NAME reduced the potency of BAY41‐2272 in the clitoral corpus cavernosum but not in the vaginal wall. BAY41‐2272 enhanced nitrergic relaxation responses only in the clitoral corpus cavernosum. Y‐27632 had no effect on nitrergic relaxations in either tissue. These results demonstrate that Y‐27632 and BAY41‐2272 elicit relaxation of the rabbit vaginal wall and clitoral corpus cavernosum.British Journal of Pharmacology (2003) 138, 287–290. doi:10.1038/sj.bjp.0705090
Attenuation of increased myocardial ischaemia‐reperfusion injury conferred by hypercholesterolaemia through pharmacological inhibition of the caspase‐1 cascade
Authors: Wang Tzung‐Dau , Chen Wen‐Jone , Mau Tzan‐Jr , Lin Jong‐Wei , Lin Wan‐Wan , Lee Yuan‐Teh 
Published: February 2003

Hypercholesterolaemia has been shown to be associated with greater myocardial ischaemia‐reperfusion injury, in which apoptosis and inflammation‐mediated necrosis both play a key role.
Caspase‐1 is involved in the activation of both apoptosis and inflammation, through the intermediate of interleukin‐1β (IL‐1β). We herein examined whether pharmacological inhibition of the caspase‐1 cascade, using Ac‐Tyr‐Val‐Ala‐Asp‐CH2Cl (Ac‐YVAD.cmk), after myocardial ischaemia have greater protective effects on myocardial ischaemia‐reperfusion injury in diet‐induced hypercholesterolaemic rabbits.
Male rabbits fed with standard chow or chow supplemented with 0.5% cholesterol and 10% coconut oil for 8 weeks were subjected to 30 min of left circumflex artery occlusion followed by 4 h of reperfusion. An intravenous bolus of Ac‐YVAD.cmk (1.6 mg kg−1) or vehicle was given 20 min after coronary occlusion.
Postischaemic administration of Ac‐YVAD.cmk markedly decreased infarct size from 26±3% to 12±2% in normally fed rabbits (P=0.005) and from 41±6% to 14±2% in cholesterol‐fed rabbits (P<0.001).
In the ischaemic non‐necrotic area, treatment with Ac‐YVAD.cmk markedly reduced the percentage of terminal deoxynucleotidyl transferase‐mediated dUTP‐biotin nick end labelling (TUNEL)‐positive cardiomyocytes from 15.5±0.8% to 2.2±0.1% in normally fed rabbits (P<0.001) and from 39.0±2.3% to 2.2±0.1% in cholesterol‐fed rabbits (P<0.001).
Ac‐YVAD.cmk treatment resulted in a reduction not only of IL‐1β and caspase‐1, but also of caspase‐3 in the ischaemic myocardium in both normally fed and cholesterol‐fed rabbits.
No differences in infarct size, the percentage of TUNEL‐positive cardiomyocytes, IL‐1β levels or activity of caspase‐1 and caspase‐3 were observed between Ac‐YVAD.cmk‐treated normally fed and cholesterol‐fed rabbits.
This study demonstrates that injection of a selective caspase‐1 inhibitor after myocardial ischaemia markedly reduced the detrimental effect conferred by hypercholesterolaemia on myocardial ischaemia‐reperfusion injury by attenuating both necrotic as well as apoptotic cell death pathways through inhibition of IL‐1β production and activation of caspase‐1 and caspase‐3.

British Journal of Pharmacology (2003) 138, 291–300. doi:10.1038/sj.bjp.0705098
Recently Duplicated Maize R2R3 Myb Genes Provide Evidence for Distinct Mechanisms of Evolutionary Divergence after Duplication
Authors: Dias Anusha P. , Braun Edward L. , McMullen Michael D. , Grotewold Erich 
Published: February 2003

Abstract
R2R3 Myb genes are widely distributed in the higher plants and comprise one of the largest known families of regulatory proteins. Here, we provide an evolutionary framework that helps explain the origin of the plant-specific R2R3 Myb genes from widely distributed R1R2R3 Mybgenes, through a series of well-established steps. To understand the routes of sequence divergence that followed Myb gene duplication, we supplemented the information available on recently duplicated maize (Zea mays) R2R3 Mybgenes (C1/Pl1 andP1/P2) by cloning and characterizingZmMyb-IF35 and ZmMyb-IF25. These two genes correspond to the recently expanded P-to-A group of maizeR2R3 Myb genes. Although the origins ofC1/Pl1 andZmMyb-IF35/ZmMyb-IF25 are associated with the segmental allotetraploid origin of the maize genome, other gene duplication events also shaped the P-to-A clade. Our analyses indicate that some recently duplicated Myb gene pairs display substantial differences in the numbers of synonymous substitutions that have accumulated in the conserved MYB domain and the divergent C-terminal regions. Thus, differences in the accumulation of substitutions during evolution can explain in part the rapid divergence of C-terminal regions for these proteins in some cases. Contrary to previous studies, we show that the divergent C termini of these R2R3 MYB proteins are subject to purifying selection. Our results provide an in-depth analysis of the sequence divergence for some recently duplicated R2R3 Myb genes, yielding important information on general patterns of evolution for this large family of plant regulatory genes.