The extent of transient, premature structure appears to correlate with the number of isoleucine, leucine, and valine (ILV) side chains that form a large sequence-local cluster involving the central β-sheet and helices α2, α3, and α4.
It is therefore possible to validate the structures by comparison with the rotameric states of isoleucine, leucine, and valine that can be derived from methyl C chemical shifts (Table 2).
Indeed, in the crystal structure of this complex, the side chain χ1 torsion angle of isoleucine 657 occupies the gauche– conformation, similar to the lower affinity complex KIX·MLL.
We find excellent agreement between the methyl C chemical shifts and the side chain rotamers that are present in the solution structures of both complexes (binary KIX·MLL and ternary KIX·MLL·pKID), suggesting the conformation that is present in the NMR structural bundles represents the most populated rotameric state of isoleucine, leucine, and valine residues in all cases.
LEA (late embryogenesis abundant) proteins functioning as molecular chaperones to maintain membrane structures, ion balance and homeostasis [ 28, 29] and enzymes for the synthesis of isoleucine (toxin degradation), serine (redox responses), and proline (an osmolyte) are encoded by memory genes.
In contrast, a β-turn conformation, almost identical to that observed in the crystal structure of pYVNV bound to the Grb2 SH2 domain, predominates for pYXNX peptides, even in the presence of isoleucine at the third position.
Taken together, these data clearly show that the conformation in the solution structures of both complexes (binary KIX·MLL and ternary KIX·MLL·pKID) represents the most populated side chain rotameric states of isoleucine, leucine, and valine residues in all cases.
The presence of essential amino acids (i.e. phenylalanine, valine, tryptophan and isoleucine) in the chemical structure of durian seed gum reinforces its nutritional value as compared to amino acid free gums.
The dynamic broadening of a subset of isoleucine and leucine side chains and the absence of protection against exchange showed that the highest energy folded state on the free-energy landscape is stabilized by a hydrophobic cluster lacking stable secondary structure.
Significant genotypic resistance was detectable after 68 weeks, indicated by a substitution of isoleucine for methionine at residue 552 (M552I).
