Molecular Biological Studies on Animal Growth Hormones

The pituitary growth hormone (GH) from various vertebrate species could be purified from crude pituitary extracts by a single‐step HPLC using a reverse‐phase C18 column. The same procedure was also useful for peptide mapping of proteins. Pharmacokinetic analysis of porcine GH revealed that it circulated in plasma with a half‐life of 2 h and that most injected GH was confined to blood and probably lymph, with a total body clearance of porcine GH around 8 ± 3 mL h⁻¹ kg⁻¹. Several GH have been sequenced by using cloning of their cDNA. The comparative analysis of these cDNA reveals the conserved structural characteristics for all vertebrate GH: 1. There are 2 disulfide bonds in the single polypeptide chain of the GH molecule which are supposedly necessary to maintain the native conformation of the hormone. 2. The invariant residues are predominantly located within the α‐helices which are also necessary to maintain the structural integrity but may not be required for species specificity. 3. The putative signal peptides of various GH deduced from the cDNA sequences show the general consensus pattern of hydrophobicity but exhibit no obvious sequence homology. These characteristics are in agreement with other signal peptides of most secretory proteins. A high‐level expression of porcine GH in E. coli was achieved by using some combination of promoter and transcriptional terminator. The expressed 22‐kDa GH was immunoreactive to the specific GH antibody and showed expected partial N‐terminal amino‐acid sequence.