Abstract
Two analogues of bovine growth hormone (BGH) have been produced in Escherichia coli by recombinant DNA techniques. In analogue Delta-1, the N-terminal alanine residue of the full-length bovine sequence is replaced by methionine. In analogue Delta-9, which is expressed at much higher levels than is Delta-1, the full-length bovine sequence is truncated at the N-terminus by eight residues and there is a serine-for-glycine substitution in the first position of the truncated protein. Both analogues, which were characterized by isoelectric focusing (i.e.f.), polyacrylamide-gel electrophoresis in the presence of SDS (SDS/PAGE), amino acid analysis and N-terminal amino acid sequence determination using combined g.l.c.-m.s., are compared with BGH isolated from pituitaries. In contrast with pituitary-derived BGH, the recombinant-derived proteins are homogeneous on SDS/PAGE and on i.e.f. In a radioimmunoassay, a radioreceptor assay and a bioassay in vivo (rat tibia), Delta-9 BGH showed very similar characteristics to the pituitary-derived hormone. Similar results have also been obtained with the Delta-1 analogue.