Molecular cloning and expression of the gene for serine hydroxymethyltransferase from an obligate methylotroph Hyphomicrobium methylovorum GM2

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Abstract
The gene encoding serine hydroxymethyltransferase (SHMT), one of the key enzymes of the one‐carbon‐compound assimilation of a methylotroph, Hyphomicrobium methylovorum GM2, and its flanking regions were isolated using a DNA fragment encoding Escherichia coli SHMT as a probe. Nucleotide sequencing of the recombinant plasmids revealed the SHMT gene codes for the 434‐amino‐acid protein with a calculated molecular mass of 46 068 Da. The amino‐acid sequence of the enzyme showed identity to the sequences of the enzymes from E. coli (55%) and rabbit liver (44%). The recombinant plasmid, which was constructed by ligation of the cloned gene and an expression vector pKK223‐3, was introduced to an SHMT‐deficient E. coli mutant ME5427 (glyA−). The transformed E. coli cells expressed SHMT, which was immunologically and enzymologically indistinguishable from the enzyme isolated from H. methylovorum GM2.