PDBsum entry 2ps9

Metal transport

PDB id: 2ps9

Contents

Protein chains

263 a.a. *

Metals

_CO ×2

Waters ×291

* Residue conservation analysis

PDB id:

2ps9

Name:

Metal transport

Title:

Structure and metal binding properties of znua, a periplasmic zinc transporter from escherichia coli

Structure:

High-affinity zinc uptake system protein znua. Chain: a, b

Source:

Escherichia coli. Organism_taxid: 562

Resolution:

2.15Å R-factor: 0.238 R-free: 0.296

Authors:

L.A.Yatsunyk,L.R.Kim,I.I.Vorontsov,A.C.Rosenzweig

Key ref:

L.A.Yatsunyk et al. (2008). Structure and metal binding properties of ZnuA, a periplasmic zinc transporter from Escherichia coli. J Biol Inorg Chem, 13, 271-288. PubMed id: 18027003

Date:

04-May-07 Release date: 05-Jun-07

Protein chains

P39172  (ZNUA_ECOLI) -  High-affinity zinc uptake system protein ZnuA from Escherichia coli (strain K12)

Seq: 310 a.a.

Struc: 263 a.a.

J Biol Inorg Chem 13:271-288 (2008)

PubMed id: 18027003

Structure and metal binding properties of ZnuA, a periplasmic zinc transporter from Escherichia coli.

L.A.Yatsunyk, J.A.Easton, L.R.Kim, S.A.Sugarbaker, B.Bennett, R.M.Breece, I.I.Vorontsov, D.L.Tierney, M.W.Crowder, A.C.Rosenzweig.

ABSTRACT

ZnuA is the periplasmic Zn(2+)-binding protein associated with the high-affinity ATP-binding cassette ZnuABC transporter from Escherichia coli. Although several structures of ZnuA and its homologs have been determined, details regarding metal ion stoichiometry, affinity, and specificity as well as the mechanism of metal uptake and transfer remain unclear. The crystal structures of E. coli ZnuA (Eco-ZnuA) in the apo, Zn(2+)-bound, and Co(2+)-bound forms have been determined. ZnZnuA binds at least two metal ions. The first, observed previously in other structures, is coordinated tetrahedrally by Glu59, His60, His143, and His207. Replacement of Zn(2+) with Co(2+) results in almost identical coordination geometry at this site. The second metal binding site involves His224 and several yet to be identified residues from the His-rich loop that is unique to Zn(2+) periplasmic metal binding receptors. Electron paramagnetic resonance and X-ray absorption spectroscopic data on CoZnuA provide additional insight into possible residues involved in this second site. The second site is also detected by metal analysis and circular dichroism (CD) titrations. Eco-ZnuA binds Zn(2+) (estimated K (d) < 20 nM), Co(2+), Ni(2+), Cu(2+), Cu(+), and Cd(2+), but not Mn(2+). Finally, conformational changes upon metal binding observed in the crystal structures together with fluorescence and CD data indicate that only Zn(2+) substantially stabilizes ZnuA and might facilitate recognition of ZnuB and subsequent metal transfer.