Conformational Properties of α-Tubulin Tail Peptide:  Implications for Tail−Body Interaction

Abstract

The carboxy-terminal segments of the alpha/beta-tubulins are flexible regions rich in acidic amino acid residues. It is generally believed that these regions play crucial roles in tubulin polymerization and interaction with many ligands, including colchicine. Exactly how these effects are exerted are not known at present. One such interesting aspect is the pH dependence of colchicine-tubulin interaction and the influence of the alpha-tail on the binding interaction. We have investigated the location of the colchicine-binding site on tubulin by docking. It has been located on the alpha/beta interface on the N-terminal side, which is also supported by much of the solution data. This location is too far from the tail regions, suggesting that influence of the tail region is transmitted by a pH-dependent conformational change. Two-dimensional NMR studies indicate that at pH 7 a 13-residue peptide corresponding to alpha-tubulin tail shows little NOE constraints, suggesting extended conformation. On the contrary, at pH 5, a relatively compact structure was deduced from the interproton NOE constraints. Pulsed field gradient measurement of diffusion constant indicates that the peptide at pH 5 is substantially faster diffusing than at pH 7. The Perrin factors calculated from diffusion data indicates that the peptide structure at pH is significantly more compact than at pH 7. Temperature coefficients of several amide protons at pH 5 fall below 5 ppb/(o)K, indicating a degree of protection. A difference is also seen in the CD spectra obtained at different pHs, consistent with the NMR data. We have investigated the probable spatial organization of the tail of the alpha-subunit of tubulin, in the high pH extended form and the low pH compact form. On the basis of correlation of pH dependence of many properties of tubulin and the conformation of the alpha-tail peptide, we propose that the intrinsic conformational preference of the tail-region modulate the tail-body interaction, which in turn has important bearing on colchicine binding properties.

Tubulin tyrosine ligase structure reveals adaptation of an ancient fold to bind and modify tubulin

“…5 f ). Moreover, solution NMR and molecular dynamics studies show that the α-tail is not fully extended, but adopts a slightly helical conformation with a ~29 Å 45 span. Thus, in the absence of large conformational changes upon binding, it is likely that TTL recognizes α-tubulin on the surface that would form the longitudinal interface in the context of the MT.…”

Anti‐mitotic activity of colchicine and the structural basis for its interaction with tubulin

“…75 Though colchicine binds at the alphabeta interface of tubulin far from its carboxy terminal end, several properties of colchicines-tubulin interactions such as pH-sensitivity, off-rate, on-rate, and the stability of the colchicines-binding site are greatly influenced by the a C-terminal of tubulin as discussed in the previous section. 67 Earlier Pal et al 76 suggested the presence of ''tail-body interaction'' between the negatively charged a-Cterminus of tubulin with the positively charged residues of the main body of tubulin. Vertebrate tubulin contains four b-tubulin classes designated as b I , b II , b III , and b IV in relative amounts of 3, 58, 25, and 13% respectively.…”

Effect of Phosphorylation on the Structure and Fold of Transactivation Domain of p53

“…For the unphosphorylated 1-39 domain, the ratio is ϳ1:7.5 (for prolate as well as oblate ellipsoids) indicating a nonspherical shape. In contrast, a completely unstructured 13-residue peptide gave an axial ratio value of ϳ1:20 by the same technique (31). A much longer peptide chain, such as p53 transactivation domain, if completely disordered, should give even higher axial ratios.…”