PDBsum entry 2vqa

Metal binding protein

PDB id: 2vqa

Contents

Protein chains

356 a.a. *

Ligands

ACT ×8

Metals

_MN ×6

Waters ×32

* Residue conservation analysis

PDB id:

2vqa

Name:

Metal binding protein

Title:

Protein-folding location can regulate mn versus cu- or zn-binding. Crystal structure of mnca.

Structure:

Sll1358 protein. Chain: a, b, c. Fragment: 35-394. Synonym: mnca. Engineered: yes

Source:

Synechocystis sp.. Organism_taxid: 1148. Strain: pcc 6803. Expressed in: escherichia coli. Expression_system_taxid: 469008.

Resolution:

2.95Å R-factor: 0.193 R-free: 0.233

Authors:

S.Tottey,K.J.Waldron,S.J.Firbank,B.Reale,C.Bessant,K.Sato,J.Gray, M.J.Banfield,C.Dennison,N.J.Robinson

Key ref:

S.Tottey et al. (2008). Protein-folding location can regulate manganese-binding versus copper- or zinc-binding. Nature, 455, 1138-1142. PubMed id: 18948958 DOI: 10.1038/nature07340

Date:

12-Mar-08 Release date: 28-Oct-08

Protein chains

P73510  (P73510_SYNY3) -  Sll1358 protein from Synechocystis sp. (strain PCC 6803 / Kazusa)

Seq: 394 a.a.

Struc: 356 a.a.

DOI no: 10.1038/nature07340

Nature 455:1138-1142 (2008)

PubMed id: 18948958

Protein-folding location can regulate manganese-binding versus copper- or zinc-binding.

S.Tottey, K.J.Waldron, S.J.Firbank, B.Reale, C.Bessant, K.Sato, T.R.Cheek, J.Gray, M.J.Banfield, C.Dennison, N.J.Robinson.

ABSTRACT

Metals are needed by at least one-quarter of all proteins. Although metallochaperones insert the correct metal into some proteins, they have not been found for the vast majority, and the view is that most metalloproteins acquire their metals directly from cellular pools. However, some metals form more stable complexes with proteins than do others. For instance, as described in the Irving-Williams series, Cu(2+) and Zn(2+) typically form more stable complexes than Mn(2+). Thus it is unclear what cellular mechanisms manage metal acquisition by most nascent proteins. To investigate this question, we identified the most abundant Cu(2+)-protein, CucA (Cu(2+)-cupin A), and the most abundant Mn(2+)-protein, MncA (Mn(2+)-cupin A), in the periplasm of the cyanobacterium Synechocystis PCC 6803. Each of these newly identified proteins binds its respective metal via identical ligands within a cupin fold. Consistent with the Irving-Williams series, MncA only binds Mn(2+) after folding in solutions containing at least a 10(4) times molar excess of Mn(2+) over Cu(2+) or Zn(2+). However once MncA has bound Mn(2+), the metal does not exchange with Cu(2+). MncA and CucA have signal peptides for different export pathways into the periplasm, Tat and Sec respectively. Export by the Tat pathway allows MncA to fold in the cytoplasm, which contains only tightly bound copper or Zn(2+) (refs 10-12) but micromolar Mn(2+) (ref. 13). In contrast, CucA folds in the periplasm to acquire Cu(2+). These results reveal a mechanism whereby the compartment in which a protein folds overrides its binding preference to control its metal content. They explain why the cytoplasm must contain only tightly bound and buffered copper and Zn(2+).

Selected figure(s)

Figure 3.
Figure 3: MncA and CucA have similar metal-sites. a, X-band electron paramagnetic resonance spectra of Cu^2+-CucA and Cu^2+-MncA. b, Residues (blue) surrounding the metal ions (pink) within each MncA cupin fold (amino-terminal, left panel; carboxy-terminal, right panel), with corresponding final 2F[o] - F[c] electron density maps contoured at 1.1 .

Figure 4.
Figure 4: MncA prefers Cu^2+ but entraps Mn^2+. a, Co-migration by gel-filtration of Cu^2+ (triangles) but not Mn^2+ (squares) after folding MncA (circles) in an excess of equimolar metals (left), and metals bound at increasing [Mn^2+] (right). b, Substitution of Mn^2+-MncA (filled triangles) or Mn^2+-CucA (open triangles) with Cu^2+. c, MncA metal-sites are buried with a channel to the surface only apparent in the C-terminal domain. Protein surfaces (yellow) are shown surrounding the MncA metal-sites (metals in pink, protein interior shaded grey). Chelating residues are those shown in Fig. 3. d, Signal peptides (not underlined), and twin arginines (bold). e, Regions of profiles containing MncA before (top) and after (bottom) addition of unfolded MncA to a periplasm extract. f, Bi-cupin MncA folds and entraps uncompetitive Mn^2+ in the cytoplasm, without competition from copper or Zn^2+, before Tat-export. Mono-cupin CucA (modelled) is exported unfolded via Sec and acquires competitive Cu^2+.

The above figures are reprinted by permission from Macmillan Publishers Ltd: Nature (2008, 455, 1138-1142) copyright 2008.

Figures were selected by an automated process.