PurT-encoded glycinamide ribonucleotide transformylase. Accommodation of adenosine nucleotide analogs within the active site
Journal of Biological Chemistry
PurT-encoded glycinamide ribonucleotide transformylase, or PurT transformylase, functions in purine biosynthesis by catalyzing the formylation of glycinamide ribonucleotide through a catalytic mechanism requiring Mg2+ATP and formate. From previous x-ray diffraction analyses, it has been demonstrated that PurT transformylase from Escherichia coli belongs to the ATP-grasp superfamily of enzymes, which are characterized by three structural motifs referred to as the A-, B-, and C-domains. In all of the ATP-grasp enzymes studied to date, the adenosine nucleotide ligands are invariably wedged between the B- and C-domains, and in some cases, such as biotin carboxylase and carbamoyl phosphate synthetase, the B-domains move significantly upon nucleotide binding. Here we present a systematic and high-resolution structural investigation of PurT transformylase complexed with various adenosine nucleotides or nucleotide analogs including Mg2+ATP, Mg2+-5′-adenylylimidodiphosphate, Mg2+-β,γ-methyleneadenosine 5′-triphosphate, Mg2+ATPγS, or Mg2+ADP. Taken together, these studies indicate that the conformation of the so-called "T-loop," delineated by Lys-155 to Gln-165, is highly sensitive to the chemical identity of the nucleotide situated in the binding pocket. This sensitivity to nucleotide identity is in sharp contrast to that observed for the "P-loop"-containing enzymes, in which the conformation of the binding motif is virtually unchanged in the presence or absence of nucleotides.
Thoden, J., Firestine, S., Benkovic, S., & Holden, H. (2002). PurT-encoded glycinamide ribonucleotide transformylase. Accommodation of adenosine nucleotide analogs within the active site. Journal of Biological Chemistry, 277 (26), 23898-23908. https://doi.org/10.1074/jbc.M202251200