Crystal structure of a major fragment of the salt-tolerant glutaminase from Micrococcus luteus K-3

• Main Authors: Kazuaki Yoshimune, Yasuo Shirakihara, Aya Shiratori, Mamoru Wakayama, Panuwan Chantawannakul, Mitsuaki Moriguchi
• Format: Journal
• Published: 2018
• Subjects: Biochemistry, Genetics and Molecular Biology
• Online Access: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=33745407589&origin=inward; http://cmuir.cmu.ac.th/jspui/handle/6653943832/61510
• Institution: Chiang Mai University

Glutaminase of Micrococcus luteus K-3 (intact glutaminase; 48 kDa) is digested to a C-terminally truncated fragment (glutaminase fragment; 42 kDa) that shows higher salt tolerance than that of the intact glutaminase. The crystal structure of the glutaminase fragment was determined at 2.4 Å resolution using multiple-wavelength anomalous dispersion (MAD). The glutaminase fragment is composed of N-terminal and C-terminal domains, and a putative catalytic serine-lysine dyad (S64 and K67) is located in a cleft of the N-terminal domain. Mutations of the S64 or K67 residues abolished the enzyme activity. The N-terminal domain has abundant glutamic acid residues on its surface, which may explain its salt-tolerant mechanism. A diffraction analysis of the intact glutaminase crystals (a twinning fraction of 0.43) located the glutaminase fragment in the unit cell but failed to turn up clear densities for the missing C-terminal portion of the molecule. © 2006 Elsevier Inc. All rights reserved.