Archives of Microbiology

, Volume 168, Issue 5, pp 345–354

Molybdate transport and regulation in bacteria

  • A. M. Grunden
  • K. T. Shanmugam

DOI: 10.1007/s002030050508

Cite this article as:
Grunden, A. & Shanmugam, K. Arch Microbiol (1997) 168: 345. doi:10.1007/s002030050508


Molybdate is transported in bacteria by a high-affinity transport system composed of a periplasmic binding protein, an integral membrane protein, and an energizer protein. These three proteins are coded by modA, modB, and modC genes, respectively. The ModA, ModB, and ModC proteins from various organisms (Escherichia coli, Haemophilus influenzae, Azotobacter vinelandii, and Rhodobacter capsulatus) are very similar. The lowest Km value reported for molybdate in the molybdate transport process is approximately 50 nM. In a mod mutant, molybdate is transported by the sulfate transport system or by a nonspecific anion transporter. Molybdate transport is tightly coupled to utilization in E. coli and Klebsiella pneumoniae, while other dinitrogen-fixing organisms appear to have a molybdenum storage protein. In all organisms studied so far, molybdate transport genes are regulated by a repressor protein, ModE. The ModE-molybdate complex binds to the sequences TAYAT (Y = T or C) in the operator/ promoter region in E. coli and prevents transcription of the modABCD operon. The ModE-molybdate complex binds to DNA as a homodimer in E. coli and possibly in other organisms as well. In R. capsulatus, however, two ModE homologues (MopAB proteins) are required for repression.

Key words Molybdate transportmodABC GenesmodE GeneMolybdate-specific repressorABCtransport systemMolybdate transport/genetics/regulationEscherichia coliAzotobacter vinelandiiRhodobacter capsulatusClostridium pasteurianum

Copyright information

© Springer-Verlag Berlin Heidelberg 1997

Authors and Affiliations

  • A. M. Grunden
    • 1
  • K. T. Shanmugam
    • 1
  1. 1.Department of Microbiology and Cell Science, 110700, University of Florida, Gainesville, FL 32611-0700, USA Tel. 352-392-2490; Fax 352-392-5922 e-mail:shan@micro.ifas.ufl.eduUS