In order to clarify the structure-activity relationship of c-Ha-
ras proteins (p 21 s) genes encoding p 21 (Val-12), p 21 (Leu-61) and p 21 (Arg-61) were synthesized by joining oligonucleotides with T 4 DNA ligase and expressed in
E. coli under the regulation of
E. coli tryptophan promoter. In addition, the gene for normal p 21 was constructed by cassette mutagenesis using restriction sites,
ClaI-
BssH II. The guanosine diphosphate (triphosphate) binding properties and guanosine triphosphatase (GTP
ase) activities of these p 21 s were examined. It was found that the guanine nucleotide binding abilities of all p 21 s produced in this study were relatively same but GTP
ase activity of activated p 21 s were significantly reduced.
Furthermore, the gene encoding novel p 21 in which the guanine nucleotide binding sites was modified was synthesized by ligation of oligonucleotides and expressed in
E.coli. Its biochemical activities are also discussed.
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