BtuB
<StructureSection load='3m8d' size='450' side='right' scene='43/439262/Cv/1' caption='E. coli BtuB complex with cobalamin (a vitamin B12 derivative), lipid, methanesulfonothioate derivative and Ca+2 ions (green) (PDB code 3m8d)'>
Function
BtuB is an outer membrane receptor found in a variety of bacteria, such as E. coli. BtuB transports vitamin B12 across the membrane of gram-negative bacteria. The transport is achieved with high affinity by the collaboration of BtuB and the periplasmic protein TonB. As an essential receptor for the cell that is constitutively expressed, it is an ideal target to be parasitized, a feature exploited by a variety of proteins such as Colicins.
Structural highlights
BtuB depends on the presence of Ca+2 ions for high affinity binding of cobalamin (a form of vitamin B12). The Ca+2 ions are coordinated to several Asp side chains.
3D structure of BtuB
Updated on 17-November-2015
2guf, 1nqe, 1nqf – EcBtuB – Escherichia coli
3m8b, 3rgm, 3rgn – EcBtuB (mutant)
3m8d - EcBtuB (mutant) + cyanocobalamin
1nqh - EcBtuB + cyanocobalamin + Ca
2ysu - EcBtuB + Colicin E2 receptor binding domain
1ujw - EcBtuB + Colicin E3 receptor binding domain
2gsk - EcBtuB + TonB C-terminal
1nqg - EcBtuB + Ca
2bto – PdBtuBA + thioredoxin – Prosthecobacter dejongeii
2btq – PdBtuBA + PdBtuBB
