Cys-92, Cys-95, and the C-Terminal 12 Residues of the Vibrio harveyi Ferric Uptake Regulator (Fur) are Functionally Inessential

다국어 초록 (Multilingual Abstract)

Ferric uptake regulator (Fur) is a global regulator involved in multiple aspects of bacterial life. The gene
encoding the Vibrio harveyi Fur (FurVh) was cloned from a pathogenic V. harveyi strain isolated from diseased
fish. FurVh shares 77% overall sequence identity with the Escherichia coli Fur (FurEc) and could complement
a mutant of FurEc. Like FurEc, FurVh possesses two cysteine residues at positions 92 and 95, yet
unlike FurEc, in which these cysteine residues constitute part of the metal ion coordination site and hence
are vital to the repressor activity, C92 and C95 of FurVh proved to be functionally inessential. Further
study identified a Vibrio Fur signature sequence, which is preserved in all the ten Vibrio Fur proteins that
have been discovered to date but in none of the non-vibrio Fur proteins. Site-directed and random mutation
analyses of the signature residues, the cysteine residues, and seven highly charged amino acid residues indicated
that D9, H32, C137, and K138 of FurVh are functionally important but D9, C137, and K138 can
be replaced by more than one functional substitutes. Systematic deletion analysis demonstrated that the
C-terminal 12 residues of FurVh are functionally inessential. These results (i) indicated that the activation
mechanism, or certain aspects of which, of FurVh is possibly different from that of FurEc; and (ii) suggested
that it is not very likely that the C-terminal 12 residues play any significant role in the activation or stability
of FurVh; and (iii) provided insights into the potential function of the local structure involving C137 and
K138.

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