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Published November 9, 2011 | Accepted Version
Journal Article Open

Classification of a Haemophilus influenzae ABC Transporter HI1470/71 through Its Cognate Molybdate Periplasmic Binding Protein, MoIA

Abstract

molA (HI1472) from H. influenzae encodes a periplasmic binding protein (PBP) that delivers substrate to the ABC transporter MolB_2C_2 (formerly HI1470/71). The structures of MolA with molybdate and tungstate in the binding pocket were solved to 1.6 and 1.7 Å resolution, respectively. The MolA-binding protein binds molybdate and tungstate, but not other oxyanions such as sulfate and phosphate, making it the first class III molybdate-binding protein structurally solved. The ~100 μM binding affinity for tungstate and molybdate is significantly lower than observed for the class II ModA molybdate-binding proteins that have nanomolar to low micromolar affinity for molybdate. The presence of two molybdate loci in H. influenzae suggests multiple transport systems for one substrate, with molABC constituting a low-affinity molybdate locus.

Additional Information

© 2011 Elsevier Ltd. Received 2 June 2011; revised 11 August 2011; Accepted 9 October 2011. Published: November 8, 2011. Available online 8 November 2011. We would like to thank Arabela Grigorescu, Ishwar Radhakrishnan, and Oded Lewinson for useful discussions. We would also like to thank Keith MacRenaris and Rebecca Marvin for assistance with ICP-MS, Yongbo Zhang for assistance with NMR titration studies, and Kaspar Locher for the initial cloning of HI1472. This work is based on research performed at SSRL, APS (21-ID-DG/ F), funded by the Department of Energy. Research at Caltech was supported in part by NIH GM045162, by the Gordon and Betty Moore for their support of the Molecular Observatory, and by the James Irvine Foundation and United Negro College Fund-Merck for postdoctoral fellowships (to H.W.P.). This work was supported in part by a grant from ACS-IRG 93-037- 15. Support for L.T.-L. was provided by NIH training Grant T32 GM008382.

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August 19, 2023
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