A new metal binding domain involved in cadmium, cobalt and zinc transport
Aaron T Smith1, Dulmini Barupala2, Timothy L Stemmler2
11] Department of Molecular Biosciences, Northwestern University, Evanston, Illinois, USA. [2] Department of Chemistry, Northwestern University, Evanston, Illinois, USA.
Abstract:
The P1B-ATPases, which couple cation transport across membranes to ATP hydrolysis, are central to metal homeostasis in all organisms. An important feature of P1B-ATPases is the presence of soluble metal binding domains (MBDs) that regulate transport activity. Only one type of MBD has been characterized extensively, but bioinformatics analyses indicate that a diversity of MBDs may exist in nature. Here we report the biochemical, structural and functional characterization of a new MBD from the Cupriavidus metallidurans P1B-4-ATPase CzcP (CzcP MBD). The CzcP MBD binds two Cd(2+), Co(2+) or Zn(2+) ions in distinct and unique sites and adopts an unexpected fold consisting of two fused ferredoxin-like domains. Both in vitro and in vivo activity assays using full-length CzcP, truncated CzcP and several variants indicate a regulatory role for the MBD and distinct functions for the two metal binding sites. Taken together, these findings elucidate a previously unknown MBD and suggest new regulatory mechanisms for metal transport by P1B-ATPases.
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