3k6u

Publication Abstract from PubMed

The trace-element oxyanion molybdate, which is required for the growth of many bacterial and archaeal species, is transported into the cell by an ATP-binding cassette (ABC) transporter superfamily uptake system called ModABC. ModABC consists of the ModA periplasmic solute-binding protein, the integral membrane-transport protein ModB and the ATP-binding and hydrolysis cassette protein ModC. In this study, X-ray crystal structures of ModA from the archaeon Methanosarcina acetivorans (MaModA) have been determined in the apoprotein conformation at 1.95 and 1.69 A resolution and in the molybdate-bound conformation at 2.25 and 2.45 A resolution. The overall domain structure of MaModA is similar to other ModA proteins in that it has a bilobal structure in which two mixed alpha/beta domains are linked by a hinge region. The apo MaModA is the first unliganded archaeal ModA structure to be determined: it exhibits a deep cleft between the two domains and confirms that upon binding ligand one domain is rotated towards the other by a hinge-bending motion, which is consistent with the 'Venus flytrap' model seen for bacterial-type periplasmic binding proteins. In contrast to the bacterial ModA structures, which have tetrahedral coordination of their metal substrates, molybdate-bound MaModA employs octahedral coordination of its substrate like other archaeal ModA proteins.

Apo and ligand-bound structures of ModA from the archaeon Methanosarcina acetivorans.,Chan S, Giuroiu I, Chernishof I, Sawaya MR, Chiang J, Gunsalus RP, Arbing MA, Perry LJ Acta Crystallogr Sect F Struct Biol Cryst Commun. 2010 Mar 1;66(Pt, 3):242-50. Epub 2010 Feb 23. PMID:20208152^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.