Prochlorococcus marinus strain PCC 9511, a picoplanktonic cyanobacterium, synthesizes the smallest urease.
The urease from the picoplanktonic oceanic Prochlorococcus marinus sp. strain PCC 9511 was purified 900-fold to a specific activity of 94.6 micromol urea min(-1) (mg protein)(-1) by heat treatment and liquid chromatography methods. The enzyme, with a molecular mass of 168 kDa as determined by gel filtration, is the smallest urease known to date. Three different subunits with apparent molecular masses of 11 kDa (gamma or UreA; predicted molecular mass 11 kDa), 13 kDa (ss or UreB; predicted molecular mass 12 kDa) and 63 kDa (alpha or UreC; predicted molecular mass 62 kDa) were detected in the native enzyme, suggesting a quaternary structure of (alphassgamma)(2). The K:(m) of the purified enzyme was determined as being 0.23 mM urea. The urease activity was inhibited by HgCl(2), acetohydroxamic acid and EDTA but neither by boric acid nor by L-methionine-DL-sulfoximine. Degenerate primers were designed to amplify a conserved region of the ureC gene. The amplification product was then used as a probe to clone a 5.7 kbp fragment of the P. marinus sp. strain PCC 9511 genome. The nucleotide sequence of this DNA fragment revealed two divergently orientated gene clusters, ureDABC and ureEFG, encoding the urease subunits, UreA, UreB and UreC, and the urease accessory molecules UreD, UreE, UreF and UreG. A putative NtcA-binding site was found upstream from ureEFG, indicating that this gene cluster might be under nitrogen control.
Palinska
Katarzyna A
KA
Unité de Physiologie Microbienne, Département de Biochimie et Génétique Moléculaire, Institut Pasteur (CNRS, URA 1129), 28 rue du Docteur Roux, 75724 Paris, France1.
Jahns
Thomas
T
Institut für Mikrobiologie, Fachrichtung 13.3, Universität des Saarlandes, D-66041 Saarbrücken, Germany2.
Rippka
Rosmarie
R
Unité de Physiologie Microbienne, Département de Biochimie et Génétique Moléculaire, Institut Pasteur (CNRS, URA 1129), 28 rue du Docteur Roux, 75724 Paris, France1.
Tandeau de Marsac
Nicole
N
Unité de Physiologie Microbienne, Département de Biochimie et Génétique Moléculaire, Institut Pasteur (CNRS, URA 1129), 28 rue du Docteur Roux, 75724 Paris, France1.
D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D000458:Cyanobacteria / Q000201:enzymology* / Q000254:growth & development; D004591:Electrophoresis, Polyacrylamide Gel; D015151:Immunoblotting; D008969:Molecular Sequence Data; D008970:Molecular Weight; D020836:Protein Structure, Quaternary; D021122:Protein Subunits; D017422:Sequence Analysis, DNA; D014510:Urease / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism
D021122:Protein Subunits; D014510:Urease