The gene fragments encoding the different N TAIL deletion proteins were cloned into the pDest14 vector (Invitrogen) to yield N-terminally histidine-tagged and C-terminally flag-tagged recombinant products, the expression of which is under the control of the T7 promoter. In all cases, most recombinant protein was recovered from the soluble fraction of bacterial lysates (Fig. 3B , lanes SN). The N TAIL deletion proteins were purified to showing the location of the a-MoRE, is given below. The inset shows the experimental scattering curve (black circles) and fit (red line) obtained by CREDO with the low-resolution model. homogeneity (>95%) in two steps: Immobilized Metal Affinity Chromatography (IMAC), and gel filtration (Fig.  3B ). The identity of the recombinant products was confirmed by IP studies using anti-N Cl25, anti-flag, and antihexahistindine tag mAbs (data not shown). As shown in Figure 3B , the three N TAIL deletion proteins migrate in SDS-PAGE with an apparent MM of either 20 kDa (N TAILD3 and N TAILD1 ) or 18 kDa (N TAILD2,3 ) (expected MMs are 14.5, 13.4, and 11.5 kDa, respectively). This abnormal migratory behavior has already been documented for N TAIL , where mass spectrometry analysis and N-terminal sequencing gave the expected results . The anomalous electrophoretic mobility is therefore due to a rather high content of acidic residues, as frequently observed in intrinsically disordered proteins (Tompa 2002) . Likewise, the behavior of the truncated N TAIL proteins can probably be accounted for by this sequence bias composition.