Microbial nickel proteins

Microorganisms have evolved to utilize nickel ions in several different enzyme systems that enable these organisms to survive and proliferate in various environments. Typically the biosynthesis of these nickel-containing enzymes are multi-step processes involving a number of accessory proteins, with one or more proteins dedicated to the delivery of the cognate nickel ion to the active site of the enzyme. This review highlights the nickel proteins dedicated to the biogenesis of [NiFe]-hydrogenase, urease, and carbon monoxide dehydrogenase, and aims to summarize our current knowledge of these unique proteins. Putative proteins that function in excess nickel storage and/or detoxification, through sequestration of considerable amount of nickel, are also discussed.