Human somatotropin. Selective removal with trypsin of residues 135-145 from the hormone molecule with no loss of biological activities.

A 11-residue segment, sequence positions 135-145, has been cleaved selectively from the human somatotropin molecule by limited digestion of the hormone with trypsin at pH 6.0 in 90% (v/v) glycerol. Differences between the tertiary structures of the native and trypsin-modified hormones have been demonstrated by circular dichroism spectroscopy. Despite these conformational differences, the biological properties of intact hormone and its modified form appeared to be very similar, as tested by two receptor-binding assays, radioimmunoassay, and the rat tibia test.