From: ncbi-seminar-admin@ncbi.nlm.nih.gov on behalf of Eugene Koonin
[koonin@golem.nlm.nih.gov]
Sent: Monday, October 28, 2002 3:40 PM
To: ncbi-seminar@golem.nlm.nih.gov
Subject: Seminar Friday the 1st

Building 45 (Natcher) 6th Floor South Conference Room
Friday November 1, 11 AM


SAM-radical enzymes

Yurii Chinenov

Howard Hughes Medical Institute, University of Michigan Medical Center 4556
MSRBII, 1150 W. Medical Center Dr. Ann Arbor, MI 48109-0650

The SAM radical enzymes utilize S-adenosylmethionine (SAM) as the source of
catalytically active deoxyadenosyl radical and are involved in a wide range
of reactions including oxidation, oxidative cyclization, C- and P-
methylation, isomerization and protein radical formation. Based on the
sequence similarities of core catalytic domains SAM radical enzymes could
be subdivided into four classes. PFL-like enzymes (PflA, PflX, AtsB, NrdG,
MoaA-like and PqqE-like) and catalyze various reactions of carbon chains
reorganization (cyclization,
isomerization) or protein radical formation. BioB-related enzymes (BioB,
LipA and ThiH) are involved in the formation of C-S bonds in various
sulfur-containing cofactors. HemN-related proteins (HemN, HemZ and
Elp3-related
acetyltransferases) participate in reactions of atypical oxidative
de-carboxylation. At last, MiaB-related proteins (MiaB, BchE and MmcD)
combine various unusual C- and P-methylases and enzymes involved in
methylthiolation of modified nucleosides in tRNAs. So far, no information
about 3D structure of SAM radical enzymes is available. Based on the remote
homology between the putative SAM binding domain and haloacid dehalogenase
it is likely that SAM catalytic core assumes Rossman-like fold. Core
SAM-radical domain is often combined with other domain such as GNAT histone
acetyltransferase, TRAM, CheY-like receiver domain, flavodoxin-like domain.
The functional implication of multidomain organization of SAM radical
enzymes is discussed. ~

--
Eugene V. Koonin, PhD
National Center for Biotechnology Information
National Library of Medicine
National Institutes of Health, Bldg. 38A, Rm. 5N503 (5th floor) 8600
Rockville Pike Bethesda, MD 20894, USA
Phone: (301)435-5913; Fax: (301)435-7794 or (301)480-9241
email koonin@ncbi.nlm.nih.gov
http://www.ncbi.nlm.nih.gov/CBBresearch/Koonin/