Motif CXCC in nitrile hydratase activator is critical for NHase biogenesis in vivo.

Nitrile hydratase (NHase) activator from Rhodococcus sp. N-771 is required for NHase functional expression. The motif 73CXCC76 in the NHase activator sequence was here revealed to be vital for its function by site-directed mutagenesis. All three substitutions of the cysteines by serines resulted in a much lower level of expression of active NHase. Furthermore, interaction between NHase activator and NHase was detected and the critical role of NHase activator was not exhibited in the cysteine oxidization process of NHase. These findings suggest NHase activator mainly participates in iron trafficking in NHase biogenesis as an iron type metallochaperone.