2jum: Difference between revisions

caption="2jum" />

'''ThrA3-DKP-insulin'''<br />

==Overview==

The contribution of the insulin A-chain to receptor binding is, investigated by photo-cross-linking and nonstandard mutagenesis. Studies, focus on the role of ValA3, which projects within a crevice between A- and, B-chains. Engineered receptor alpha-subunits containing specific protease, sites ("midi-receptors") are employed to map the site of, photo-cross-linking by an analog containing a photo-activatable A3 side, chain (para-azido-Phe; Pap). The probe cross-links to a C-terminal peptide, (residues 703-719 of the receptor A isoform; KTFEDYLHNVVFVPRPS) containing, side chains critical for hormone binding (bold); the corresponding segment, of the holoreceptor was previously shown to cross-link to a PapB25-insulin, analog. Because Pap is larger than Val and so may protrude beyond the, A3-associated crevice, we investigated analogs containing A3 substitutions, comparable in size to Val: Thr, allo-Thr, and alpha-amino-butyric acid, (Aba). Substitutions were introduced within an engineered monomer. Whereas, previous studies of smaller substitutions (GlyA3 and SerA3) encountered, nonlocal conformational perturbations, NMR structures of the present, analogs are similar to wild-type insulin; the variant side chains are, accommodated within a native-like crevice with minimal distortion., Receptor-binding activities of AbaA3 and allo-ThrA3 analogs are reduced at, least tenfold; the activity of ThrA3-DKP-insulin is reduced fivefold. The, hormone-receptor interface is presumably destabilized either by a packing, defect (AbaA3) or by altered polarity (allo-ThrA3 and ThrA3). Our results, provide evidence that ValA3 - a site of mutation causing diabetes mellitus, - contacts the insert-domain-derived tail of the alpha-subunit in a, hormone-receptor complex.

==About this Structure==

==Reference==

[[Category: thra3]]