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bioRxiv · 10.1101/412205

The atypical thiol-disulfide exchange protein α-DsbA2 from Wolbachia pipientis is a homotrimeric disulfide isomerase

Walden, P. M.·Whitten, A. E.·Lakshmanane, P.·Halili, M.·Heras, B.·King, G.·Martin, J. L.
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Abstract

DiSulfide Bond (DSB) oxidative folding enzymes are master regulators of virulence localized to the periplasm of many Gram-negative bacteria. The archetypal DSB machinery from Escherichia coli K12 has a dithiol oxidizing redox relay pair (DsbA/B), a disulfide isomerizing redox relay pair (DsbC/D) and specialist reducing enzymes DsbE and DsbG that also interact with DsbD. By contrast the Gram-negative bacterium Wolbachia pipientis encodes just three DSB enzymes. Two of these -DsbA1 and -DsbB form a redox relay pair analogous to E. coli DsbA/B. The third enzyme -DsbA2 incorporates a DsbA-like sequence but does not interact with -DsbB. In comparison with other DsbA enzymes, -DsbA2 has [~]50 extra N-terminal residues. The crystal structure of -DsbA2{Delta}N, the N-terminally truncated form in which these residues are removed confirms the DsbA-like nature of this domain. However, -DsbA2 does not have DsbA-like activity: it is structurally and functionally different as a consequence of its N-terminal residues. First, -DsbA2 is a powerful disulfide isomerase and a poor dithiol oxidase - ie its role is to shuffle rather than introduce disulfide bonds. Moreover, small-angle X-ray scattering of -DsbA2 reveals a homotrimeric arrangement. Our results allow us to draw conclusions about the factors required for functionally equivalent enzymatic activity across structurally diverse protein architectures.

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Walden, P. M., Whitten, A. E., Lakshmanane, P., Halili, M., Heras, B., King, G., Martin, J. L.. 2018-09-08. The atypical thiol-disulfide exchange protein α-DsbA2 from Wolbachia pipientis is a homotrimeric disulfide isomerase. https://doi.org/10.1101/412205

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