NMR study on solution structure of the site-specific mutant Leu48----Ala transforming growth factor alpha

The NMR spectra of the Leu48----Ala mutant of human transforming growth factor alpha were compared to that of the wild-type. All chemical shift changes are less than or equal to 0.02 ppm with the exception of resonances associated with residues 47, 48 and 50 (all less than or equal to 0.07 ppm). Minimal changes were observed for NOEs associated with residues Val1 to His45. The weakening of some NOEs associated with the region Ala46-Ala50 may suggest a slightly increased flexibility for this region. Refinement of the previously calculated wild-type structures using distance constraints derived from the L48A mutant had little overall effect. Leu48-Ala50 is ill-defined for both wild-type and mutant proteins. These results suggest that Leu48 has no structural role and thus must be an important factor in the protein-receptor interface.