| 摘要 |
A method for preparing polypeptides in bacteria with an alanine rather than a methionine at the N-terminus. The DNA sequence expressed has an alanine codon immediately following from at least one methionine codon, and allows for the expression of polypeptides having the amino acid sequence essentially the same as such naturally occurring eucaryotic protein as various bovine and porcine somatotropin species. In another important embodiment, the invention provides a class of compositions comprising certain valine-containing somatropin species which increase milk production in lactating mammals to a significantly greater extent than otherwise-identical leucine somatotropin species.
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