Recruitment of a novel zinc-bound transcriptional factor by a bacterial HMGA-type protein is required for regulating multiple processes in Myxococcus xanthus

Mol Microbiol. 2006 Aug;61(4):910-26. doi: 10.1111/j.1365-2958.2006.05289.x.


Enhanceosome assembly in eukaryotes often requires high mobility group A (HMGA) proteins. In prokaryotes, the only known transcriptional regulator with HMGA-like physical, structural and DNA-binding properties is Myxococcus xanthus CarD. Here, we report that every CarD-regulated process analysed also requires the product of gene carG, located immediately downstream of and transcriptionally coupled to carD. CarG has the zinc-binding H/C-rich metallopeptidase motif found in archaemetzincins, but with Q replacing a catalytically essential E. CarG, a monomer, binds two zinc atoms, shows no apparent metallopeptidase activity, and its stability in vivo absolutely requires the cysteines. This indicates a strictly structural role for zinc-binding. In vivo CarG localizes to the nucleoid but only if CarD is also present. In vitro CarG shows no DNA-binding but physically interacts with CarD via its N-terminal and not HMGA domain. CarD and CarG thus work as a single, physically linked, transcriptional regulatory unit, and if one exists in a bacterium so does the other. Like zinc-associated eukaryotic transcriptional adaptors in enhanceosome assembly, CarG regulates by interacting not with DNA but with another transcriptional factor.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Carotenoids / biosynthesis
  • Conserved Sequence
  • DNA, Bacterial / metabolism
  • Gene Deletion
  • Genetic Complementation Test
  • HMGA Proteins / genetics
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Myxococcus xanthus / genetics
  • Myxococcus xanthus / growth & development
  • Myxococcus xanthus / metabolism*
  • Open Reading Frames
  • Protein Binding
  • Sequence Alignment
  • Trans-Activators / metabolism*
  • Transcription Factors / chemistry
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*
  • Zinc / metabolism*


  • Bacterial Proteins
  • CarD protein, Myxococcus xanthus
  • DNA, Bacterial
  • HMGA Proteins
  • Trans-Activators
  • Transcription Factors
  • Carotenoids
  • Zinc