 R. E. Humbel

R. E. Humbel coauthored experimental work identifying the chemical structure of human insulin-like growth factors with E. Rinderknecht. Their 1978 study determined the complete sequence of serum-derived insulin-like growth factor 1: a single chain of seventy amino acid residues connected by three disulfide bonds.^[ref]

The comparison with proinsulin connected a biological activity to a molecular relationship. Corresponding regions resembled the insulin chains, while an intervening connecting segment remained in the growth factor. Conserved residues were compatible with a related folded structure; sequence similarity was evidence for that inference, not an atomic structure determination.^[ref]

This research illustrates why a bioassay and sequence analysis complement one another. Two preparations can produce similar responses without containing identical proteins. Establishing residue order and covalent connections provides an independent way to distinguish related signaling molecules.