Crystal structure of pyruvate kinase from Geobacillus stearothermophilus.
The pyruvate kinase (PK) from a moderate thermophile, Geobacillus stearothermophilus, is an allosteric enzyme activated by AMP and ribose 5-phosphate but not fructose 1, 6-bisphosphate (FBP), which is a common activator of PKs. It has an extra C-terminal sequence (ECTS), which contains a highly conserved phosphoenolpyruvate (PEP) binding motif, but its function and structure remain unclear. To elucidate the structural characteristics of the effector-binding site and the ECTS, the crystal structure of the C9S/C268S mutant of the enzyme was determined at 2.4 A resolution. The crystal belonged to space group P6(2)22, with unit cell parameters a, b = 145.97 A, c = 118.03 A. The enzyme was a homotetramer and its overall domain structure was similar to the previously solved structures except that the ECTS formed a new domain (C' domain). The structure of the C' domain closely resembled that of the PEP binding domain of maize pyruvate phosphate dikinase. A sulphate ion was found in a pocket in the effector-binding C domain. This site corresponds to the 6-phosphate group-binding site in yeast PK bound FBP and seems to be the effector-binding site. Through comparison of the structure of the putative effector-binding site to that of the FBP binding site of the yeast enzyme, the structural basis of the effector specificity of the G. stearothermophilus PK is discussed.
Department of Food and Nutritional Sciences, University of Shizuoka, Yada 52-1, Shizuoka 422-8526, Japan.
Kenichiro
K
Suzuki
Sohei
S
Ito
Akiko
A
Shimizu-Ibuka
Hiroshi
H
Sakai
D000249:Adenosine Monophosphate / Q000737:chemistry; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D001411:Geobacillus stearothermophilus / Q000201:enzymology*; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D009154:Mutation; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011770:Pyruvate Kinase / Q000737:chemistry*; D012267:Ribosemonophosphates / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D003313:Zea mays / Q000201:enzymology
D012267:Ribosemonophosphates; D000249:Adenosine Monophosphate; C031626:ribose-5-phosphate; D011770:Pyruvate Kinase