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Classification of a Haemophilus influenzae ABC transporter HI1470/71 through its cognate molybdate periplasmic

Leidamarie Tirado-Lee1, Allen Lee, Douglas C Rees

  • 1Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA.

Structure (London, England : 1993)
|November 15, 2011
PubMed

Insights

The first structural analysis of a class III molybdate-binding protein, MolA from H. influenzae, reveals low-affinity binding for molybdate and tungstate. This suggests H. influenzae utilizes multiple transport systems for essential elements.

Area of Science:

  • Biochemistry
  • Structural Biology
  • Microbiology

Background:

  • H. influenzae utilizes specific transport systems for essential nutrients.
  • Periplasmic binding proteins (PBPs) are crucial for substrate delivery to ABC transporters.
  • MolA (HI1472) is a PBP involved in the MolABC transporter system.

Purpose of the Study:

  • To determine the structure of the MolA protein from H. influenzae.
  • To investigate the substrate-binding properties of MolA for molybdate and tungstate.
  • To characterize MolA as a class III molybdate-binding protein.

Main Methods:

  • X-ray crystallography was used to solve the structures of MolA.
  • Structures were determined with molybdate and tungstate bound to the protein.
  • Binding affinities were assessed and compared to other molybdate-binding proteins.

Main Results:

  • The crystal structures of MolA with molybdate and tungstate were solved at 1.6 and 1.7 Å resolution.
  • MolA specifically binds molybdate and tungstate, excluding sulfate and phosphate.
  • This represents the first structural solution for a class III molybdate-binding protein.
  • MolA exhibits a lower binding affinity (∼100 μM) for molybdate and tungstate compared to class II ModA proteins.

Conclusions:

  • The molABC system in H. influenzae represents a low-affinity molybdate transport locus.
  • The existence of two molybdate loci suggests H. influenzae has multiple systems for transporting a single substrate.
  • Structural insights into MolA provide a foundation for understanding molybdate transport mechanisms.

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