Crystal structure of human arginase I at 1.29 A resolution and exploration of inhibition in the immune responseDi Costanzo, L., Sabio, G., Mora, A., Rodriguez, P.C., Ochoa, A.C., Centeno, F., Christianson, D.W.
(2005) Proc Natl Acad Sci U S A 102: 13058-13063
- PubMed: 16141327
- DOI: https://doi.org/10.1073/pnas.0504027102
- Primary Citation of Related Structures:
- PubMed Abstract:
Human arginase I is a potential target for therapeutic intervention in diseases linked to compromised l-arginine homeostasis. Here, we report high-affinity binding of the reaction coordinate analogue inhibitors 2(S)-amino-6-boronohexanoic acid (ABH, Kd = 5 nM) and S-(2-boronoethyl)-l-cysteine (BEC, Kd = 270 nM) to human arginase I, and we report x-ray crystal structures of the respective enzyme-inhibitor complexes at 1.29- and 1.94-A resolution determined from crystals twinned by hemihedry. The ultrahigh-resolution structure of the human arginase I-ABH complex yields an unprecedented view of the binuclear manganese cluster and illuminates the structural basis for nanomolar affinity: bidentate inner-sphere boronate-manganese coordination interactions and fully saturated hydrogen bond networks with inhibitor alpha-amino and alpha-carboxylate groups. These interactions are therefore implicated in the stabilization of the transition state for l-arginine hydrolysis. Electron density maps also reveal that active-site residue H141 is protonated as the imidazolium cation. The location of H141 is such that it could function as a general acid to protonate the leaving amino group of l-ornithine during catalysis, and this is a revised mechanistic proposal for arginase. This work serves as a foundation for studying the structural and chemical biology of arginase I in the immune response, and we demonstrate the inhibition of arginase activity by ABH in human and murine myeloid cells.
Roy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104-6323, USA.