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Crystal Structure of Thermotoga maritima 0065, a Member of the IclR Transcriptional Factor Family

2002; Elsevier BV; Volume: 277; Issue: 21 Linguagem: Inglês

10.1074/jbc.m112171200

1083-351X

Rongguang Zhang, Youngchang Kim, T. Skarina, Steven Beasley, Roman A. Laskowski, C.H. Arrowsmith, A.M. Edwards, A. Joachimiak, Alexei Savchenko,

Glycosylation and Glycoproteins Research

Members of the IclR family of transcription regulators modulate signal-dependent expression of genes involved in carbon metabolism in bacteria and archaea. The Thermotoga maritima TM0065 gene codes for a protein (TM-IclR) that is homologous to the IclR family. We have determined the crystal structure of TM-IclR at 2.2 A resolution using MAD phasing and synchrotron radiation. The protein is composed of two domains: the N-terminal DNA-binding domain contains the winged helix-turn-helix motif, and the C-terminal presumed regulatory domain is involved in binding signal molecule. In a proposed signal-binding site, a bound Zn(2+) ion was found. In the crystal, TM-IclR forms a dimer through interactions between DNA-binding domains. In the dimer, the DNA-binding domains are 2-fold related, but the dimer is asymmetric with respect to the orientation of signal-binding domains. Crystal packing analysis showed that TM-IclR dimers form a tetramer through interactions exclusively by signal-binding domains. A model is proposed for binding of IclR-like factors to DNA, and it suggests that signal-dependent transcription regulation is accomplished by affecting an oligomerization state of IclR and therefore its affinity for DNA target.