Sandbox Reserved 497

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This Sandbox is Reserved from 13/03/2012, through 01/06/2012 for use in the course "Proteins and Molecular Mechanisms" taught by Robert B. Rose at the North Carolina State University, Raleigh, NC USA. This reservation includes Sandbox Reserved 451 through Sandbox Reserved 500.
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Dimethylsulfoniopropionate-Dependent Demethylase (DmdA)Dimethylsulfoniopropionate-Dependent Demethylase (DmdA)

Dimethylsulfoniopropionate-Dependent Demethylase (DmdA), 3TFH

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IntroductionIntroduction

Dimethylsulfoniproprionate (DMSP) is a common metabolite produced by marine microorganisms and it acts as a significant carbon and sulfur source for marine bacteria. Degradation of DMSP occurs by either the cleavage pathway or the demethylation pathway [1]. The demethylation pathway is characterized by the conversion of DMSP into methylmercaptopropionate (MMPA). Dimethylsulfoniopropionate-Dependendent Demethylase (DmdA) is the first enzyme in the demethylation pathway and facilitates this conversion by acting as a methyl transferase.

StructureStructure

Panel A is an image of the protein dimer DmdA. Panel B contains the three labeled domains and the active cleft site of DmdA. Image obtained directly from Schuller et al.

The structure of DmdA has recently been solved through the use of X-Ray diffraction [2]. The structure is a protein dimer composed of 369 amino acid residues and contains three distinct domains and four , two of which are sodium ions and two of which are glycerol. The structure is composed of both and and has regions dispersed throughout the protein. The active site cleft is located between domain 1 and domain 2. Each domain contains unique identifying structural components. is characterized by a Greek Key surrounded by three alpha-helices while contains a five-stranded antiparallel beta-sheet with alpha-helices on either side. Alternatively, has a distorted jellyroll formation. While DmdA belongs to the glycine cleavage T-protein (GcvT) family there is only approximately . These few conserved amino acids likely interact with tetrahydrofolate (THF), which is a cofactor required by DmdA as well as many other enzymes in the GcvT family. While the exact binding mechanism of THF to the active site cleft DmdA is still unknown, it appears as if the mechanism is unlike the general mechanism used by enzymes in the GcvT family and is unique to DmdA alone. In particular, amino acid residues may be essential for THF binding as they assist in ring stacking as well as have the potential for hydrogen bonding. Similarly, research is still being conducted in order to determine the amino acids essential for the binding of the substrate, DMSP, to DmdA. So far it appears as if amino acid residues are important due to their potential for hydrogen bonding.

Mechanism of ActionMechanism of Action

The specific mechanism of DmdA is still being investigated. However, a mechanism was recently proposed [3]

Proposed mechanism

Possible ApplicationsPossible Applications

ReferencesReferences

  1. Reisch, C.R., Moran, M.A., Whitman, W.B. (2008). Dimethylsulfoniopropionate-Dependent Demethylase (DmdA) from Pelagibacter ubique and Silicibacter pomeroyi. J. Bacteriol. 190: 8018-8024.
  2. Image from the RCSB PDB (www.pdb.org) of PDB ID 3TFH (Schuller, D.J., Reisch, C.R., Moran, M.A., Whitman, W.B., Lanzilotta, W.N. (2012) Structures of dimethylsulfoniopropinate-dependent demethylase from the marine organism pelagabacter ubique. Protein Sci. 21: 289-298).
  3. Schuller, D.J., Reisch, C.R., Moran, M.A., Whitman, W.B., Lanzilotta, W.N. (2012) Structures of dimethylsulfoniopropinate-dependent demethylase from the marine organism pelagabacter ubique. Protein Sci. 21: 289-298.

Proteopedia Page Contributors and Editors (what is this?)Proteopedia Page Contributors and Editors (what is this?)

OCA, Kara Tinker