PDBsum entry 2iz7

Metal transport

PDB id: 2iz7

Contents

Protein chains

162 a.a. *

Waters ×232

* Residue conservation analysis

PDB id:

2iz7

Name:

Metal transport

Title:

Structure of moco carrier protein from chlamydomonas reinhardtii

Structure:

Moco carrier protein. Chain: a, b. Engineered: yes

Source:

Chlamydomonas reinhardtii. Organism_taxid: 3055. Expressed in: escherichia coli. Expression_system_taxid: 562.

Biol. unit:

Tetramer (from PDB file)

Resolution:

2.32Å R-factor: 0.185 R-free: 0.263

Authors:

K.Fischer,A.Llamas,M.Tejada-Jimenez,N.Schrader,J.Kuper,R.R.Mendel, E.Fernandez,G.Schwarz

Key ref:

K.Fischer et al. (2006). Function and structure of the molybdenum cofactor carrier protein from Chlamydomonas reinhardtii. J Biol Chem, 281, 30186-30194. PubMed id: 16873364 DOI: 10.1074/jbc.M603919200

Date:

25-Jul-06 Release date: 27-Jul-06

Protein chains

Q8RV61  (Q8RV61_CHLRE) -  Molybdenum cofactor carrier protein from Chlamydomonas reinhardtii

Seq: 165 a.a.

Struc: 162 a.a.

DOI no: 10.1074/jbc.M603919200

J Biol Chem 281:30186-30194 (2006)

PubMed id: 16873364

Function and structure of the molybdenum cofactor carrier protein from Chlamydomonas reinhardtii.

K.Fischer, A.Llamas, M.Tejada-Jimenez, N.Schrader, J.Kuper, F.S.Ataya, A.Galvan, R.R.Mendel, E.Fernandez, G.Schwarz.

ABSTRACT

The molybdenum cofactor (Moco) forms the catalytic site in all eukaryotic molybdenum enzymes and is synthesized by a multistep biosynthetic pathway. The mechanism of transfer, storage, and insertion of Moco into the appropriate apo-enzyme is poorly understood. In Chlamydomonas reinhardtii, a Moco carrier protein (MCP) has been identified and characterized recently. Here we show biochemical evidence that MCP binds Moco as well as the tungstate-substituted form of the cofactor (Wco) with high affinity, whereas molybdopterin, the ultimate cofactor precursor, is not bound. This binding selectivity points to a specific metal-mediated interaction with MCP, which protects Moco and Wco from oxidation with t((1/2)) of 24 and 96 h, respectively. UV-visible spectroscopy showed defined absorption bands at 393, 470, and 570 nm pointing to ene-diothiolate and protein side-chain charge transfer bonds with molybdenum. We have determined the crystal structure of MCP at 1.6 Angstrom resolution using seleno-methionated and native protein. The monomer constitutes a Rossmann fold with two homodimers forming a symmetrical tetramer in solution. Based on conserved surface residues, charge distribution, shape, in silico docking studies, structural comparisons, and identification of an anionbinding site, a prominent surface depression was proposed as a Moco-binding site, which was confirmed by structure-guided mutagenesis coupled to substrate binding studies.

Selected figure(s)

Figure 3.
FIGURE 3. Structure of C. reinhardtii MCP. A, ribbon presentation of the MCP monomer (MCP2 chain A) with -strands colored in gold and -helices shown in green. Residues Gly-70 and Ile-76 that border the stretch of delocalized residues are highlighted. B and C, top view (B) and side view (C)ofthe tetramer in ribbon presentation (MCP2). the color code of the monomers is as follows: A, red;B, green;C, blue;D, yellow. The monomers C and D were generated by applying crystallographic symmetry operations. Interface I depicts the hydrophobic contacts between A and B and C and D, and Interface II describes the more hydrophilic contacts of B and C and A-D. D, superposition of MCP2 (chain B, green) with T. thermophilus HB8 hypothetical protein TT1465 (Protein Data Bank code 1WEK chain F, gray), B. subtilis putative lysine decarboxylase (Protein Data Bank code 1T35 chain B, light pink), and A. thaliana lysine decarboxylase-like protein from gene AT2G37210 (Protein Data Bank code 2A33 chain A, lilac). Figures were generated with MOLSCRIPT (52) and rendered with POVRAY.

Figure 5.
FIGURE 5. The Moco-binding site. A ribbon presentation of MCP (MCP2 chain B, green) and homologous structures is shown, as shown (compare Fig. 3D). Cocrystallized phosphate (Protein Data Bank code 1WEK) and sulfate molecules (Protein Data Bank codes 2A33, 1T35) are depicted in stick mode and color-coded according to the protein structure (compare Fig. 3). The top-scored Moco model from GOLD docking studies is shown in green. Three structures have disordered residues in a similar region (MCP, 70-77; Protein Data Bank code 1WEK, 100-101-107; and Protein Data Bank code 2A33, 78-87). Figures were prepared as in Fig. 3.

The above figures are reprinted by permission from the ASBMB: J Biol Chem (2006, 281, 30186-30194) copyright 2006.

Figures were selected by the author.