To initiate X-ray crystallographic structural studies, we created a BHMT expression construct for use in Escherichia coli that has a polyhistidine purification tag with no extraneous protein, usually found in commercial vectors, between the tag and protein sequence. Elevated levels of plasma homocysteine may be a risk factor for the development of vascular disease; however, whether BHMT has a significant role in the regulation of plasma levels of homocysteine remains to be determined.