Download MendeleyStructural and biochemical characterization of Siw14: A protein-tyrosine phosphatase fold that metabolizes inositol pyrophosphates.
Wang, H., Gu, C., Rolfes, R.J., Jessen, H.J., Shears, S.B.(2018) J Biol Chem 293: 6905-6914
- PubMed: 29540476
- DOI: https://doi.org/10.1074/jbc.RA117.001670
- Primary Citation of Related Structures:
6BYF - PubMed Abstract:
Inositol pyrophosphates (PP-InsPs) are "energetic" intracellular signals that are ubiquitous in animals, plants, and fungi; structural and biochemical characterization of PP-InsP metabolic enzymes provides insight into their evolution, reaction mechanisms, and regulation. Here, we describe the 2.35-Å-resolution structure of the catalytic core of Siw14, a 5-PP-InsP phosphatase from Saccharomyces cerevisiae and a member of the protein tyrosine-phosphatase (PTP) superfamily. Conclusions that we derive from structural data are supported by extensive site-directed mutagenesis and kinetic analyses, thereby attributing new functional significance to several key residues. We demonstrate the high activity and exquisite specificity of Siw14 for the 5-diphosphate group of PP-InsPs. The three structural elements that demarcate a 9.2-Å-deep substrate-binding pocket each have spatial equivalents in PTPs, but we identify how these are specialized for Siw14 to bind and hydrolyze the intensely negatively charged PP-InsPs. ( a ) The catalytic P-loop with the C X 5 R(S/T) PTP motif contains additional, positively charged residues. ( b ) A loop between the α5 and α6 helices, corresponding to the Q-loop in PTPs, contains a lysine and an arginine that extend into the catalytic pocket due to displacement of the α5 helix orientation through intramolecular crowding caused by three bulky, hydrophobic residues. ( c ) The general-acid loop in PTPs is replaced in Siw14 with a flexible loop that does not use an aspartate or glutamate as a general acid. We propose that an acidic residue is not required for phosphoanhydride hydrolysis.
Organizational Affiliation:
From the Inositol Signaling Group, Signal Transduction Laboratory, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709, huanchen.wang@nih.gov.
