Insights into the reaction of protein-tyrosine phosphatase 1B: crystal structures for transition state analogs of both catalytic steps.
Catalysis by protein-tyrosine phosphatase 1B (PTP1B) occurs through a two-step mechanism involving a phosphocysteine intermediate. We have solved crystal structures for the transition state analogs for both steps. Together with previously reported crystal structures of apo-PTP1B, the Michaelis complex of an inactive mutant, the phosphoenzyme intermediate, and the product complex, a full picture of all catalytic steps can now be depicted. The transition state analog for the first catalytic step comprises a ternary complex between the catalytic cysteine of PTP1B, vanadate, and the peptide DADEYL, a fragment of a physiological substrate. The equatorial vanadate oxygen atoms bind to the P-loop, and the apical positions are occupied by the peptide tyrosine oxygen and by the PTP1B cysteine sulfur atom. The vanadate assumes a trigonal bipyramidal geometry in both transition state analog structures, with very similar apical O-O distances, denoting similar transition states for both phosphoryl transfer steps. Detailed interactions between the flanking peptide and the enzyme are discussed.
Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322-0300, USA.
Tiago A S
TA
Brandão
Alvan C
AC
Hengge
Sean J
SJ
Johnson
D002384:Catalysis; D018360:Crystallography, X-Ray; D006801:Humans; D017433:Protein Structure, Secondary; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1 / Q000737:chemistry* / Q000378:metabolism; D013329:Structure-Activity Relationship
C516607:PTPN1 protein, human; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1