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

• Main Authors: Yoshimune K., Shirakihara Y., Shiratori A., Wakayama M., Chantawannakul P., Moriguchi M.
• Format: Article
• Language: English
• Published: 2014
• Online Access: http://www.scopus.com/inward/record.url?eid=2-s2.0-33745407589&partnerID=40&md5=8150627818cdf7b1367792e2df09d85d; http://cmuir.cmu.ac.th/handle/6653943832/5095
• 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.