2IZ6

Structure of the Chlamydomonas rheinhardtii Moco Carrier Protein

Summary for 2IZ6

• Entry DOI: 10.2210/pdb2iz6/pdb
• Related: 2IZ5 2IZ7
• Descriptor: MOLYBDENUM COFACTOR CARRIER PROTEIN (2 entities in total)
• Functional Keywords: molybdenum cofactor, metal transport
• Biological source: CHLAMYDOMONAS REINHARDTII
• Total number of polymer chains: 2
• Total formula weight: 35777.34

Authors

Fischer, K.,Llamas, A.,Tejada-Jimenez, M.,Schrader, N.,Kuper, J.,Mendel, R.R.,Fernandez, E.,Schwarz, G. (deposition date: 2006-07-25, release date: 2006-07-26, Last modification date: 2023-12-13)

Primary citation

Fischer, K.,Llamas, A.,Tejada-Jimenez, M.,Schrader, N.,Kuper, J.,Ataya, F.S.,Galvan, A.,Mendel, R.R.,Fernandez, E.,Schwarz, G.
Function and Structure of the Molybdenum Cofactor Carrier Protein from Chlamydomonas Reinhardtii.
J.Biol.Chem., 281:30186-, 2006

PubMed 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.

PubMed: 16873364
DOI: 10.1074/JBC.M603919200

Experimental method

X-RAY DIFFRACTION (1.6 Å)