expression of constructs encompassing the full-length, just the catalytic and regulatory domain (amino acids 38-644), and encompassing the regulatory domain and part of the linker region (amino acids 348-656)
chromosomal copy of MET13 is replaced by an Arabidopsis thaliana MTHFR cDNA (AtMTHFR-1) or by a chimeric sequence (Chimera-1) comprising the yeast N-terminal domain and the AtMTHFR-1 C-terminal domain. Chimera-1 uses both NADH and NADPH and is insensitive to S-adenosyl-L-methionine. Engineered yeast expressing Chimera-1 accumulates 140fold more S-adenosyl-L-methionine and 7fold more methionine than does the wild-type and grows normally. Yeast expressing AtMTHFR-1 accumulates 8fold more S-adenosyl-L-methionine