While more than half of newly-synthesized wild-type proinsulin [or mutants classically associated with adult-onset diabetes, or the proinsulin-G(C28)R variant] were recovered as the native disulfide isomer, only one third of MIDY mutants (35.1%±7.2%) could be recovered as any kind of monomeric isomer (Fig. 1Aupper panels). This evidence concerns the gene INS and type 2 diabetes mellitus.