• Click the edit this page tab at the top. Save the page after each step, then edit it again.
• Click the 3D button (when editing, above the wikitext box) to insert Jmol.
• show the Scene authoring tools, create a molecular scene, and save it. Copy the green link into the page.
• Add a description of your scene. Use the buttons above the wikitext box for bold, italics, links, headlines, etc.

More help: Help:Editing

For more help, look at this link: http://www.proteopedia.org/wiki/index.php/Help:Getting_Started_in_Proteopedia

Vitamin B12 Binding Protein

General Information

Structure

Vitamin B12-binding Protein contains two α/β domains, which are linked by a rigid α-helix that spans the length of the protein. Each domain consist of a central five-stranded β-sheet surrounded by helices. It resembles the ferrichrome binding protein FhuD by its bi-lobed fold. The vitamin conformation, or “base-on” conformation is where the bound vitamin B12 can be found within the deep acidic cleft formed at the interface between the two BtuF lobes (3). It is bound by the enzymes methionine synthase, methylmalonyl-coA mutase, and glutamate mutase. Within these enzymes the pseudonucleotide tail of B12 is extended and the nitrogen of a nearby histidine side chain is able to act as an axial ligand to the cobalt. The "base-on" conformation of the BtuF-bound B12 allows the N3B nitrogen of the dimethylbenzimidazole (DMB) base to serve as an axial ligand to the central cobalt atom.

Iron and b12 uptake are mediated by the conservation among binding proteins and ABC transporters of two surface glutamates from BtuF that interact with arginine residues on the periplasmic surface of the BtuCD transporter. This is thought to play a role in docking and the transmission of conformational changes (2).

The C-terminal domain is structurally similar to the B12-binding domain that can be found in various enzymes. Conformational change that may involve an increase in domain mobility is said to be a result of unwinding of an α-helix located in the C-terminal domain. This unwinding would occur upon the binding on BtuF with BtuC and would thus result in the release into the transport cavity. Overall, it is the free mobility of the C-terminal domain that is essential to the release of BtuF necessary for the completeion of the transport cycle (3).

Function

Organism

Mechanism of Action

Medical Implications

Brittany A. Gabriel, Student, North Carolina State University, Raleigh, NC - United States. Biochemistry.