Monellin (MNEI) at 1.15 angstrom resolution

• Authors: J.R. Hobbs, University of Manchester; S.D. Munger, University of Maryland; Graeme Conn, Emory University
• Journal Title: Acta Crystallographica Section F: Structural Biology and Crystallization Communications
• Volume: Volume 63, Number 3
• Publisher: International Union of Crystallography | 2007-03-01, Pages 162-167
• Type of Work: Article | Final Publisher PDF
• Publisher DOI: http://doi.org/10.1107/S1744309107005271
• Subjects: Chemistry, Biochemistry; Health Sciences, General
• Keywords: Science & Technology; Life Sciences & Biomedicine; Physical Sciences; Biochemical Research Methods; Biochemistry & Molecular Biology; Biophysics; Crystallography; BIOCHEMICAL RESEARCH METHODS; BIOCHEMISTRY & MOLECULAR BIOLOGY; BIOPHYSICS; CRYSTALLOGRAPHY; SWEET PROTEIN MONELLIN; SINGLE-CHAIN MONELLIN; SOLID-PHASE SYNTHESIS; CRYSTAL-STRUCTURE; ACTIVE-SITE; RECEPTOR; MODELS; TASTE; STABILITY; THAUMATIN

Abstract

The X-ray crystal structure of a single-chain monellin protein (MNEI) has been determined at 1.15 Å resolution. The model was refined to convergence employing anisotropic displacement parameters and riding H atoms to produce a final model with Rwork and Rfree values of 0.132 and 0.162, respectively. The crystal contains a single MNEI protein in the asymmetric unit and unusually lacks the dimer interface observed in all previous crystal structures of monellin and its single-chain derivatives. The high resolution allowed a more detailed view of MNEI than previously possible, with 38 of the 96 residues modelled with alternative side-chain conformations, including four core residues Thr12, Cys41, Leu62 and Ile75. Four stably bound negative ions were also located, providing new insight into potential electrostatic interactions of MNEI with the largely negatively charged surface of the sweet taste receptor T1R2-T1R3.