Ghorbel Sofiane, Smirnov Aleksey, Chouayekh Hichem, Sperandio Brice, Esnault Catherine, Kormanec Jan, Virolle Marie-Joelle
Department of Microbiology, Immunology and Molecular Genetics, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, Kansas 66160, USA.
J Bacteriol. 2006 Sep;188(17):6269-76. doi: 10.1128/JB.00202-06.
The ppk gene of Streptomyces lividans encodes an enzyme catalyzing, in vitro, the reversible polymerization of the gamma phosphate of ATP into polyphosphate and was previously shown to play a negative role in the control of antibiotic biosynthesis (H. Chouayekh and M. J. Virolle, Mol. Microbiol. 43:919-930, 2002). In the present work, some regulatory features of the expression of ppk were established and the polyphosphate content of S. lividans TK24 and the ppk mutant was determined. In Pi sufficiency, the expression of ppk was shown to be low but detectable. DNA gel shift experiments suggested that ppk expression might be controlled by a repressor using ATP as a corepressor. Under these conditions, short acid-soluble polyphosphates accumulated upon entry into the stationary phase in the wild-type strain but not in the ppk mutant strain. The expression of ppk under Pi-limiting conditions was shown to be much higher than that under Pi-sufficient conditions and was under positive control of the two-component system PhoR/PhoP. Under these conditions, the polyphosphate content of the cell was low and polyphosphates were reproducibly found to be longer and more abundant in the ppk mutant strain than in the wild-type strain, suggesting that Ppk might act as a nucleoside diphosphate kinase. In light of our results, a novel view of the role of this enzyme in the regulation of antibiotic biosynthesis in S. lividans TK24 is proposed.
变铅青链霉菌的ppk基因编码一种酶,该酶在体外催化ATP的γ磷酸可逆聚合成多聚磷酸盐,并且先前已表明其在抗生素生物合成的调控中起负作用(H. Chouayekh和M. J. Virolle,《分子微生物学》43:919 - 930,2002)。在本研究中,确定了ppk表达的一些调控特征,并测定了变铅青链霉菌TK24和ppk突变体的多聚磷酸盐含量。在磷充足的情况下,ppk的表达显示较低但可检测到。DNA凝胶迁移实验表明,ppk的表达可能受一种以ATP作为辅阻遏物的阻遏物控制。在这些条件下,野生型菌株进入稳定期后积累了短的酸溶性多聚磷酸盐,而ppk突变体菌株中则没有。在磷限制条件下,ppk的表达显示远高于磷充足条件下的表达,并且受双组分系统PhoR/PhoP的正调控。在这些条件下,细胞的多聚磷酸盐含量较低,并且可重复地发现ppk突变体菌株中的多聚磷酸盐比野生型菌株中的更长且更丰富,这表明Ppk可能作为核苷二磷酸激酶起作用。根据我们的结果,提出了关于该酶在变铅青链霉菌TK24抗生素生物合成调控中作用的新观点。