Publisher： John Wiley & Sons Inc
E-ISSN： 1744-3091|61|8|779-781
ISSN： 1744-3091
Source： Acta Crystallographica Section F, Vol.61, Iss.8, 2005-08, pp. : 779-781
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Abstract
Sigma factors are transcription‐regulatory proteins that bind to RNA polymerase and facilitate promoter recognition. The so‐called extracytoplasmic function sigma factors help a bacterium to respond to environmental conditions. Mycobacterium tuberculosis SigC (σC) is an extracytoplasmic sigma factor that is essential for lethality in a mouse model of infection and is conserved in all pathogenic mycobacterial species. This protein consists of two domains that are connected by an ∼25‐amino‐acid linker. The N‐terminal domain contains the σ2 DNA‐binding motif, whereas the σ4 motif is located in the C‐terminal domain. Native σC did not yield diffraction‐quality crystals. However, two of its domains have been cloned, expressed and crystallized: (12.3 kDa) and (7.5 kDa). The crystals belong to the hexagonal space group P61, with unit‐cell parameters a = b = 85.28, c = 79.63 Å, and native X‐ray diffraction data were collected from this domain to 2.7 Å on an in‐house X‐ray home source. The crystals belong to the cubic space group F23, with unit‐cell parameters a = b = c = 161.21 Å. X‐ray diffraction data were collected from this domain to 3.1 Å, also on an in‐house X‐ray source.
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