Site-directed disulfide bonding reveals an interaction site between energy-coupling protein TonB and BtuB, the outer membrane cobalamin transporter
Site-directed disulfide bonding reveals an interaction site between energy-coupling protein TonB and BtuB, the outer membrane cobalamin transporter
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DOI：
10.1073/pnas.96.19.10673
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发表时间：
1999-09-14
影响因子：
11.1
通讯作者：
Kadner, RJ
中科院分区：
文献类型：
--
作者：
Cadieux, N;Kadner, RJ
维生素Bit在大肠杆菌外膜上的运输与铁-铁载体复合物的运输一样，是一个主动运输过程，需要特定的外膜转运体BtuB、质子动力和跨质周能量偶联蛋白TonB。TonB与两种依赖TonB的铁载体转运体之间的相互作用此前已通过甲醛交联检测到。位点定向二硫交联证明了BtuB的保守区域（称为TonB-box）和TonB的一部分（以前认为是TonB-box突变抑制位点）之间的接触。TonB-box中二硫键与交替残基的特定模式允许推断这两个蛋白质片段之间接触区域的构象和平行方向。当BtuB装载底物时，几个位置的交联增加，并且由于BtuB中存在取代物而改变交联模式，从而导致tonb不偶联表型。因此，这种交联过程反映了参与主动运输耦合的蛋白质相互作用。
Transport of vitamin Bit across the outer membrane of Escherichia coli, like that of iron-siderophore complexes, is an active transport process requiring a specific outer membrane transporter BtuB, the proton motive force, and the trans-periplasmic energy coupling protein TonB, Interaction between TonB and two of the TonB-dependent siderophore transporters has been detected previously by formaldehyde crosslinking, Here, site-directed disulfide crosslinking demonstrates contact between a conserved region of BtuB, called the TonB-box, and a portion of TonB, previously implicated as the site of suppressors of TonB-box mutations. The specific pattern of disulfide bonding to alternating residues in the TonB-box allowed deduction of the conformation and parallel orientation of the contact region between these two protein segments. Crosslinking at several positions was increased when BtuB was loaded with substrate, and the crosslinking pattern was altered by the presence of substitutions in BtuB that cause a TonB-uncoupled phenotype. This crosslinking process thus reflects protein interactions that are involved in coupling to active transport.