Nickel in Microbial Physiology - From Single Proteins to Complex Trafficking Systems:Nickel Import/Export

In response to the low nickel availability in most natural environments, bacteria have developed high-affinity transporters to meet cell needs for the synthesis of nickel-containing enzymes. Two main categories of such importers are known: single polypeptide permeases and multicomponent members of the ATP-binding cassette (ABC) family. In addition, bacteria possess different kinds of nickel efflux systems to regulate nickel homeostasis and avoid toxic buildup of nickel concentration in the cell. In this chapter we review the recent advances concerning nickel import/export mechanisms that allow bacteria to fulfill metalloenzyme biosynthesis while circumventing the toxicity of this element.