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.
Brandão
Tiago A S
TA
Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322-0300, USA.
Hengge
Alvan C
AC
Johnson
Sean J
SJ
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