JBC, Vol. 250, Issue 16, 6291-6295, Aug, 1975
Proinsulin: a proposed three-dimensional structure
C. R. Snell and D. G. Smyth
Empirical analysis of the primary structures of 10 mammalian C-peptides has
indicated a conservation of conformation. The positioning of the C-peptide
in the proinsulin molecule is essentially defined by the proposed secondary
structure, the covalent connection to the A1 and B30 residues of insulin
and the requirement that C-peptide lies against the exposed surface of the
insulin hexamer, allowing a three-dimensional structure for proinsulin to
be predicted. Conserved residues in the C-peptide are proximate to residues
in insulin that are also conserved, suggesting that interactions between
these residues are highly probable. Residues in insulin thought to be
important for biological activity are principally those that interact with
the C-peptide residues. The role of the C-peptide region in proinsulin in
preventing expression of insulin activity and for nucleation of the folding
of the prohormone are discussed.