Crystal structure of a major fragment of the salt-tolerant glutaminase from Micrococcus luteus K-3.
Glutaminase of Micrococcus luteus K-3 (intact glutaminase; 48kDa) is digested to a C-terminally truncated fragment (glutaminase fragment; 42kDa) that shows higher salt tolerance than that of the intact glutaminase. The crystal structure of the glutaminase fragment was determined at 2.4A 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.
Yoshimune
Kazuaki
K
Research Institute of Genome-based Biofactory, National Institute of Advanced Industrial Science and Technology (AIST), Tsukisamu-Higashi 2-17-2-1, Toyohira-ku, Sapporo 062-8517, Japan. k.yoshimune@aist.go.jp
Shirakihara
Yasuo
Y
Shiratori
Aya
A
Wakayama
Mamoru
M
Chantawannakul
Panuwan
P
Moriguchi
Mitsuaki
M
D001426:Bacterial Proteins / Q000737:chemistry; D003460:Crystallization; D018360:Crystallography, X-Ray; D005972:Glutaminase / Q000737:chemistry*; D016982:Micrococcus luteus / Q000201:enzymology*; D008958:Models, Molecular; D010446:Peptide Fragments / Q000737:chemistry*; D011487:Protein Conformation
D001426:Bacterial Proteins; D010446:Peptide Fragments; D005972:Glutaminase; C477762:salt-tolerant glutaminase