Structural and biochemical characterization of a halophilic archaeal alkaline phosphatase.
Phosphate is an essential component of all cells that must be taken up from the environment. Prokaryotes commonly secrete alkaline phosphatases (APs) to recruit phosphate from organic compounds by hydrolysis. In this study, the AP from Halobacterium salinarum, an archaeon that lives in a saturated salt environment, has been functionally and structurally characterized. The core fold and the active-site architecture of the H. salinarum enzyme are similar to other AP structures. These generally form dimers composed of dominant beta-sheet structures sandwiched by alpha-helices and have well-accessible active sites. The surface of the enzyme is predicted to be highly negatively charged, like other proteins of extreme halophiles. In addition to the conserved core, most APs contain a crown domain that strongly varies within species. In the H. salinarum AP, the crown domain is made of an acyl-carrier-protein-like fold. Different from other APs, it is not involved in dimer formation. We compare the archaeal AP with its bacterial and eukaryotic counterparts, and we focus on the role of crown domains in enhancing protein stability, regulating enzyme function, and guiding phosphoesters into the active-site funnel.
Wende
Andy
A
Department of Membrane Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.
Johansson
Patrik
P
Vollrath
Ronnald
R
Dyall-Smith
Mike
M
Oesterhelt
Dieter
D
Grininger
Martin
M
D000469:Alkaline Phosphatase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D019617:Halobacterium salinarum / Q000201:enzymology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment
D019843:Archaeal Proteins; D000469:Alkaline Phosphatase