Evidence for a role of a vicinal dithiol in the transport of gamma-butyrobetaine in Agrobacterium sp.

An Agrobacterium sp. isolated from soil is able to use gamma-butyrobetaine as its sole source of carbon and nitrogen. The involvement of thiol groups for active transport of gamma-butyrobetaine was investigated by use of the thiol alkylating reagent N-ethylmaleimide (NEM) and the dithiol specific reagent phenylarsine oxide (PAO). Both reagents strongly inhibited gamma-butyrobetaine uptake, but also induced the release of the accumulated substrate, suggesting that the transport system either contains a dithiol-dependent protein or that a small thiol-containing molecule is implicated in the uptake phenomenon.