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Vitamin B12 Binding Protein

General Information

Structure

Vitamin B12-binding Protein contains two α/β domains, which are linked by a rigid α-helix. It resembles the ferrichrome binding protein FhuD by its bi-lobed fold and is a 28kDa protein. The vitamin conformation, or “base-on” conformation is where the bound B12 can be found within the deep acidic cleft formed at the interface of between the two lobes (3).

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 as 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.