Recruitment of a novel zinc-bound transcriptional factor by a bacterial HMGA-type protein is required for regulating multiple processes in Myxococcus xanthus.
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.
Peñalver-Mellado
Marcos
M
Departamento de Genética y Microbiología, Facultad de Biología, Universidad de Murcia, Murcia 30100, Spain.
García-Heras
Francisco
F
Padmanabhan
S
S
García-Moreno
Diana
D
Murillo
Francisco J
FJ
Elías-Arnanz
Montserrat
M
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002338:Carotenoids / Q000096:biosynthesis; D017124:Conserved Sequence; D004269:DNA, Bacterial / Q000378:metabolism; D017353:Gene Deletion; D005816:Genetic Complementation Test; D024003:HMGA Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D016941:Myxococcus xanthus / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D016366:Open Reading Frames; D011485:Protein Binding; D016415:Sequence Alignment; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015032:Zinc / Q000378:metabolism*
D001426:Bacterial Proteins; C100589:CarD protein, Myxococcus xanthus; D004269:DNA, Bacterial; D024003:HMGA Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D002338:Carotenoids; D015032:Zinc