The globins of Campylobacter jejuni.

Campylobacter jejuni is a zoonotic Gram-negative bacterial pathogen that is exposed to reactive nitrogen species, such as nitric oxide, from a variety of sources. To combat the toxic effects of this nitrosative stress, C. jejuni upregulates a small regulon under the control of the transcriptional activator NssR, which positively regulates the expression of a single-domain globin protein (Cgb) and a truncated globin protein (Ctb). Cgb has previously been shown to detoxify nitric oxide, but the role of Ctb remains contentious. As C. jejuni is amenable to genetic manipulation, and its globin proteins are easily expressed and purified, a combination of mutagenesis, complementation, transcriptomics, spectroscopic characterisation and structural analyses has been used to probe the regulation, function and structure of Cgb and Ctb. This ability to study Cgb and Ctb with such a multi-pronged approach is a valuable asset, especially since only a small fraction of known globin proteins have been functionally characterised.