Structure and function of cytoplasmic serine hydroxymethyltransferase from Pichia pastoris.

Serine hydroxymethyltransferase (SHMT) catalyzes the interconversion of serine and glycine, which is crucial for one carbon metabolism. Here, we report the first crystal structure of cytoplasmic SHMT from Pichia pastoris (pcSHMT) diffracted to 2.5 Å resolution in space group C2221. PcSHMT was a contaminant with our target protein expressed in Pichia pastoris and confirmed by mass spectrometry. The overall structure of pcSHMT is similar to Human mitochondrial SHMT and different to E. coli SHMT. Interestingly, the oligomerization of pcSHMT expressed in eukaryotic or prokaryotic system differs significantly and is regulated by pyridoxal-5′-phosphate. Our results revealed a close evolutionary relationship between Pichia pastoris and Human mitochondria.