[Cloning and expression of the E. coli serine hydroxymethyltransferase gene (glyA)]

The E. coli K12 glyA gene(13 kb), encoding serine hydroxymethyltransferase (SHMT), has been cloned in the plasmid vector pBR329 using insertion inactivation and complementation test. Subcloning of segments of the original insert (13 kb) into plasmids pBR322, pBR329 and pSMY901 established that a 2.6 kb PstI-EcoR fragment carries the glyA gene. The 12 strains of transforments containing recombined plasmid. were obtained. SHMT and glyA gene product level in strains carrying glyA plasmids were different. No SHMT activity was observed in host strains. The glyA gene products for JM109(pSM13), K12(pSM13), K12(pSM14) and K12(pSM15) account for 15.7%, 15.4%, 11.8%, and 9.48% of the total dissoluble cell protein, respectively.