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SELECTIVE CLEAVAGE AT THE SINGLE TRYPTOPHAN RESIDUE IN BOVINE SOMATOTROPIN BY 2‐(2‐NITROPHENYLSULFENYL)‐3‐METHYL‐3‘‐BROMOINDOLEMINE

1978; Wiley; Volume: 11; Issue: 1 Linguagem: Inglês

10.1111/j.1399-3011.1978.tb02820.x

0367-8377

Richard A. Houghten, Choh Hao Li,

Growth Hormone and Insulin-like Growth Factors

SELECTIVE CLEAVAGE AT THE SINGLE TRYPTOPHAN RESIDUE IN BOVINE SOMATOTROPIN BY 2‐(2‐NITROPHENYLSULFENYL)‐3‐METHYL‐3′‐BROMOINDOLEMINE The single tryptophan residue at position 86 in bovine somatotropin has been cleaved by the use of 2‐(2‐nitrophenylsulfenyl)‐3‐methyl‐3′‐bromoindolemine. This reaction was carried out with native bovine growth hormone as well as its reduced and alkylated derivative. When performed on the intact hormone, followed by the reduction and alkylation of the disulfides to liberate the two fragments, the cleavage reaction yielded the fragment containing residues 87–191 in a monomeric state. The other fragment, containing residues 1–86, could only be obtained in a highly aggregated form admixed with other material. When the cleavage reaction was carried out on the reduced and alkylated hormone, both the N‐terminal fragment of reduced‐carbamidomethylated bovine somatotropin as a monomer and the C‐terminal fragment as a dimer were obtained in 35–40% yield. Since the cleavage reaction also oxidized methionine to methionine sulfoxide, the sulfoxides were reduced back to the methionine with N‐methylmercapto acetamide. In this manner the following new derivatives and fragments of bovine somatotropin have been prepared: completely reduced and alkylated hormone, reduced and alkylated hormone with its methionines and tryptophan oxidized, reduced and alkylated hormone with its tryptophan oxidized, the N‐terminal fragment of the hormone containing residues 1–86 with its methionine and tryptophan oxidized, the C‐terminal fragment containing residues 87–191, both with its methionines oxidized and in their native state. The chemical and physical properties of these derivatives and fragments have been determined. Biological activity in the rat tibia was found to be negligible for all derivatives and fragments.