| 摘要 |
Somatotropin modifications are described that have unexpected enhancements in conformational and chemical stability without loss of bioactivity. Alterations of these characteristics are obtained via modification of somatotropins by site-directed mutagenesis. These changes increase the storage stability of these proteins. Exemplary modifications include poreine somatotropins having histidine and arginine substitutions for glutamine and histidine at positions 19 and 20, respectively (Q19H, H20R), having glutamic acid substituted for phenylalanine at position 52 (F52E), and having glutamic acid substituted for leucine at position 137 (1137E). The modified somatotropins are useful to enhance growth characteristics in animal species, e.g., to increase the leanto-fat ratio in pigs and milk production in cows.
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