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Distribution of ATPase and ATP-to-ADP phosphate exchange activities in magnesium chelatase subunits of Chlorobium vibrioforme and Synechocystis PCC6803






Archives of Microbiology 171(3): 146-150, Feb

Distribution of ATPase and ATP-to-ADP phosphate exchange activities in magnesium chelatase subunits of Chlorobium vibrioforme and Synechocystis PCC6803

Insertion of magnesium into protoporphyrin IX is a complex ATP-dependent reaction catalysed by the enzyme Mg-chelatase. Three separate proteins (Mg-chelatase subunits), designated as D, H and I, are involved in the chelation reaction. The genes encoding the Mg-chelatase subunits of the green sulfur bacterium Chlorobium vibrioforme and of the cyanobacterium Synechocystis strain PCC6803 were expressed in Escherichia coli. The recombinant proteins were purified, tested for ATPase and phosphate exchange activities, and compared with the activities of the corresponding subunits of Rhodobacter sphaeroides. The Synechocystis strain PCC6803 I subunit and the C. vibrioforme H and I subunits hydrolysed ATP at the rates of 2.0, 1.8 and 0.16 nmol (mg protein)-1 min-1, respectively. The ATPase activity of the C. vibrioforme H subunit was similar to that reported for the R. sphaeroides H subunit. The Synechocystis strain PCC6803 H subunit failed to hydrolyse ATP. The I subunit of Synechocystis strain PCC6803 and C. vibrioforme catalysed a transfer of PO4 from ATP to ADP (exchange activity) at the rate of 1.75 +/- 0.15 nmol (mg protein)-1 min-1. This exchange rate was 300-fold lower than that reported for the R. sphaeroides I subunit. The PO4 exchange activities were correlated with the presence of the sequence GXRGTGKSTXVRALA in the primary structure of the three I subunits. Mg-chelatase activity was reconstituted by combining the three subunits of the same bacterium [rates of 41-89 pmol Mg-deuteroporphyrin (mg protein)-1 min-1]. Heterologous subunit combinations resulted in low or no Mg-chelatase activity.

Accession: 010483660

PMID: 10201094

DOI: 10.1007/s002030050692

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Related references

Petersen, B.L.; Kannangara, C.G.; Henningsen, K.W., 1999: Distribution of ATPase and ATP-to-ADP phosphate exchange activities in magnesium chelatase subunits of Chlorobium vibrioforme and Synechocystis PCC6803. Insertion of magnesium into protoporphyrin IX is a complex ATP-dependent reaction catalysed by the enzyme Mg-chelatase. Three separate proteins (Mg-chelatase subunits), designated as D, H and I, are involved in the chelation reaction. The genes en...

Jensen, P.E.; Gibson, L.C.; Hunter, C.N., 1999: ATPase activity associated with the magnesium-protoporphyrin IX chelatase enzyme of Synechocystis PCC6803: evidence for ATP hydrolysis during Mg2+ insertion, and the MgATP-dependent interaction of the ChlI and ChlD subunits. Insertion of Mg2+ into protoporphyrin IX catalysed by the three-subunit enzyme magnesium-protoporphyrin IX chelatase (Mg chelatase) is thought to be a two-step reaction, consisting of activation followed by Mg2+ chelation. The activation step requ...

Reid, J.D.; Hunter, C.Neil., 2004: Magnesium-dependent ATPase activity and cooperativity of magnesium chelatase from Synechocystis sp. PCC6803. The first committed step in chlorophyll biosynthesis is catalyzed by magnesium chelatase, a complex enzyme with at least three substrates, cooperative Mg(2+) activation, and free energy coupling between ATP hydrolysis and metal-ion chelation. A de...

Jensen, P.E.; Gibson, L.C.; Hunter, C.N., 1998: Determinants of catalytic activity with the use of purified I, D and H subunits of the magnesium protoporphyrin IX chelatase from Synechocystis PCC6803. The I, D and H subunits (ChlI, ChlD and ChlH respectively) of the magnesium protoporphyrin IX chelatase from Synechocystis have been purified to homogeneity as a result of the overexpression of the encoding genes in Escherichia coli and the produc...

Hansson, M.; Kannangara, C.G.mini, 1997: ATPases and phosphate exchange activities in magnesium chelatase subunits of Rhodobacter sphaeroides. Three separate proteins, BchD, BchH, and BchI, together with ATP, insert magnesium into protoporphyrin IX. An analysis of ATP utilization by the subunits revealed the following: BchH catalyzed ATP hydrolysis at the rate of 0.9 nmol per min per mg...

Hansson, M.; Kannangara, C.G., 1997: ATPases and phosphate exchange activities in magnesium chelatase subunits of Rhodobacter sphaeroides. Three separate proteins, BchD, BchH, and BchI, together with ATP, insert magnesium into protoporphyrin IX. An analysis of ATP utilization by the subunits revealed the following: BchH catalyzed ATP hydrolysis at the rate of 0.9 nmol per min per mg...

Petersen, B.L.; Jensen, P.E.; Gibson, L.C.; Stummann, B.M.; Hunter, C.N.; Henningsen, K.W., 1998: Reconstitution of an active magnesium chelatase enzyme complex from the bchI, -D, and -H gene products of the green sulfur bacterium Chlorobium vibrioforme expressed in Escherichia coli. Magnesium-protoporphyrin chelatase, the first enzyme unique to the (bacterio)chlorophyll-specific branch of the porphyrin biosynthetic pathway, catalyzes the insertion of Mg2+ into protoporphyrin IX. Three genes, designated bchI, -D, and -H, from...

Jensen, P.E.; Gibson, L.C.; Henningsen, K.W.; Hunter, C.N., 1996: Expression of the chlI, chlD, and chlH genes from the Cyanobacterium synechocystis PCC6803 in Escherichia coli and demonstration that the three cognate proteins are required for magnesium-protoporphyrin chelatase activity. Magnesium-protoporphyrin chelatase catalyzes the first step unique to chlorophyll synthesis: the insertion of Mg-2+ into protoporphyrin IX. Genes from Synechocystis sp. PCC6803 with homology to the bchI and bchD genes of Rhodobacter sp. were clone...

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