Open AccessMolecular and cellular characterisation of the zinc uptake ( Z nu) system of N ostoc punctiforme
Author(s) -
Hudek Lee,
Pearson Leanne A.,
Michalczyk Agnes,
Neilan Brett A.,
Ackland M. Leigh
Publication year - 2013
Publication title -
fems microbiology ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.377
H-Index - 155
eISSN - 1574-6941
pISSN - 0168-6496
DOI - 10.1111/1574-6941.12153
Subject(s) - biology , operon , mutant , complementation , repressor , zinc , biochemistry , zinc finger , escherichia coli , gene , transmembrane domain , microbiology and biotechnology , transcription factor , chemistry , organic chemistry
Metal homoeostasis in cyanobacteria is based on uptake and export systems that are controlled by their own regulators. This study characterises the zinc uptake ( Z nu) system in N ostoc punctiforme . The system was found to comprise of three subunits in an ACB operon: a Z n 2+ ‐binding protein ( Z nu A 18), a transmembrane domain ( Z nu B ) and an ATP ase ( Z nu C ). These proteins are encoded within the znu operon regulated by a zinc uptake transcription repressor ( Z ur). Interestingly, a second Z n 2+ ‐binding protein ( Z nu A 08) was also identified at a distal genomic location. Interactions between components of the Z nu ACB system were investigated using knockouts of the individual genes. The znu A 08 − , znu A 18 − , znu B − and znu C − mutants displayed overall reduced znu ACB transcript levels, suggesting that all system components are required for normal expression of znu genes. Zinc uptake assays in the Z n 2+ ‐binding protein mutant strains showed that the disruption of znu A 18 had a greater negative effect on zinc uptake than disruption of znu A 08 . Complementation studies in E scherichia coli indicated that both znu A 08 and znu A 18 were able to restore zinc uptake in a znu A − mutant, with znu A 18 permitting the highest zinc uptake rate. The N . punctiforme zur was also able to complement the E . coli zur − mutant.