Download MendeleyThe maturation mechanism of gamma-glutamyl transpeptidases: Insights from the crystal structure of a precursor mimic of the enzyme from Bacillus licheniformis and from site-directed mutagenesis studies.
Pica, A., Chi, M.C., Chen, Y.Y., d'Ischia, M., Lin, L.L., Merlino, A.(2015) Biochim Biophys Acta 1864: 195-203
- PubMed: 26536828
- DOI: https://doi.org/10.1016/j.bbapap.2015.10.006
- Primary Citation of Related Structures:
4Y23 - PubMed Abstract:
γ-Glutamyl transpeptidases (γ-GTs) are members of N-terminal nucleophile hydrolase superfamily. They are synthetized as single-chain precursors, which are then cleaved to form mature enzymes. Basic aspects of autocatalytic processing of these pro-enzymes are still unknown. Here we describe the X-ray structure of the precursor mimic of Bacillus licheniformis γ-GT (BlGT), obtained by mutating catalytically important threonine to alanine (T399A-BlGT), and report results of autoprocessing of mutants of His401, Thr415, Thr417, Glu419 and Arg571. Data suggest that Thr417 is in a competent position to activate the catalytic threonine (Thr399) for nucleophilic attack of the scissile peptide bond and that Thr415 plays a major role in assisting the process. On the basis of these new structural results, a possible mechanism of autoprocessing is proposed. This mechanism, which guesses the existence of a six-membered transition state involving one carbonyl and two hydroxyl groups, is in agreement with all the available experimental data collected on γ-GTs from different species and with our new Ala-scanning mutagenesis data.
Organizational Affiliation:
Department of Chemical Sciences, University of Naples Federico II, Via Cintia, Naples I-80126, Italy; Istituto di Biostrutture e Bioimmagini, CNR, Via Mezzocannone, 16, Naples 80133, Italy.
