Role of the phenylalanine B25 side chain in directing insulin interaction with its receptor. Steric and conformational effects.

Structure-based stabilization of insulin as a therapeutic protein assembly via enhanced aromatic–aromatic interactions

“…Because standard MM calculations employ a simplified model of aromatic systems (i.e. approximating their quantum-mechanical (QM) properties via partial atomic charges (19,20)), ab initio QM simulations of the aromatic cluster and their incorporation in QM/MM simulations (21) promise to establish a rigorous foundation for therapeutic protein design, including further optimization through incorporation of modified or nonstandard amino acids (22)(23)(24). The present results suggest that insulin's conserved aromatic cluster can provide a natural laboratory for such foundational analysis and its therapeutic translation.…”

“…residues (Val 715 , Pro 716 , Arg 717 , and Pro 718 ) that can only accommodate trigonal ␥-carbons (22). B25-related aromaticaromatic interactions are limited due to the peripheral location of this residue (Fig.…”

Calculating the absolute binding free energy of the insulin dimer in an explicit solvent

“… 2,3 For example, how to figure out the process by which one insulin monomer binds to another and how to reduce the affinity between them. For the first problem, despite many studies having been done in this field, 4–8 the real binding mechanism of the insulin monomers is still unclear. 9 In order to solve the second problem, some fast-acting insulin analogues with low affinities have been exploited, such as lispro insulin (Lys B28 , Pro B29 ), 10 and insulin glulisine (Lys B3 , Glu B29 ).…”

Understanding insulin and its receptor from their three-dimensional structures

“…In particular, insulin's receptor engagement was deduced to be mediated by what was called the hormone's “classical” receptor-binding region—residues ValB12, TyrB16, GlyB23, PheB24, PheB25, TyrB26, GlyA1, GlnA5, TyrA19 and AsnA21. This region overlaps insulin's dimer-forming surface ( Figure 1 D), and suggestions of its involvement in receptor binding arose initially from its conservation across species [ 41 ] but was subsequently supported by a wealth of data derived from mutant insulins (see, for example, [ [42] , [43] , [44] , [45] , [46] , [47] , [48] ]). Confirmation also arose from chemical cross-linking studies, wherein it was shown that residue PheB25 (and ValA3) of insulin could be cross-linked to the C-terminal region of the receptor α chain [ 49 , 50 ] and that residues TyrB16 and PheB24 of insulin could be cross-linked to the N-terminal region of the receptor α chain [ 51 , 52 ] (see below for the definition of the receptor α and β chains).…”