# Crystallization and preliminary X-ray diffraction studies of two domains of a bilobed extra-cytoplasmic function sigma factor SigC from Mycobacterium tuberculosis

Thakur, Krishan G and Gopal, B (2005) Crystallization and preliminary X-ray diffraction studies of two domains of a bilobed extra-cytoplasmic function sigma factor SigC from Mycobacterium tuberculosis. In: Acta Crystallographica Section F, 61 (Part 8). 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 extra cytoplasmic function sigma factors help a bacterium to respond to environmental conditions. Mycobacterium tuberculosis SigC (\sigma C) 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 $\sigma_{2}$ DNA-binding motif, whereas the $\sigma_{4}$ motif is located in the C-terminal domain. Native $\sigma^{C}$ did not yield diffraction-quality crystals. However, two of its domains have been cloned, expressed and crystallized: $\sigma^{C}_{2}$ (12.3 kDa) and $\sigma^{C}_{4}$ (7.5 kDa). The $\sigma^{C}_{2}$ crystals belong to the hexagonal space group $P6_{1}$, with unit-cell parameters a = b = 85.28, c = 79.63 Angstrom, and native X-ray diffraction data were collected from this domain to 2.7 Angstrom 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 . X-ray diffraction data were collected from this domain to 3.1 Angstrom, also on an in-house X-ray source.

Item Type: Journal Article Copyright for this article belongs to John Wiley and Sons. extracytoplasmic function sigma factor;transcription regulation;SigC;RNA polymerase Division of Biological Sciences > Molecular Biophysics Unit 10 Nov 2005 09 Jan 2012 07:22 http://eprints.iisc.ernet.in/id/eprint/3977