Ogunnariwo J A, Schryvers A B
Department of Microbiology and Infectious Diseases, University of Calgary, Calgary, Alberta, Canada T2N 4N1.
J Bacteriol. 2001 Feb;183(3):890-6. doi: 10.1128/JB.183.3.890-896.2001.
Analysis of bovine respiratory isolates of Pasteurella multocida demonstrated that six of nine strains tested were capable of growth dependent upon bovine transferrin and of specifically binding ruminant transferrins. A single 82-kDa protein was affinity isolated from the P. multocida strains with immobilized bovine transferrin. In contrast to what has been observed in other species, binding of this protein to immobilized transferrin was specifically blocked by the N-lobe subfragment of bovine transferrin. A single gene encoding the 82-kDa protein was flanked by a leucyl-tRNA synthetase gene and an IS1060 element, in contrast to other species where genes encoding the two receptor proteins (TbpB and TbpA) are found in an operonic arrangement. A similar gene arrangement was observed in all of the receptor-positive strains, in spite of the observation that they belonged to different genomic groups. Analysis of the deduced amino acid sequence of the receptor protein indicated that it is a member of the TonB-dependent outer membrane receptor family, and although it is related to transferrin and lactoferrin receptor proteins (TbpAs and LbpAs) from other species, it differs substantially from other members of this group. Amino acid alignments suggest that the reduced size (20 kDa smaller) of the P. multocida TbpA is primarily due to the absence of larger predicted external loops. Collectively these results suggest that P. multocida has a single, novel receptor protein (TbpA) that is capable of efficiently mediating iron acquisition from bovine transferrin without the involvement of a second receptor protein (TbpB).
多杀性巴氏杆菌牛呼吸道分离株的分析表明，所检测的9株菌株中有6株能够依赖牛转铁蛋白生长，并能特异性结合反刍动物转铁蛋白。用固定化牛转铁蛋白从多杀性巴氏杆菌菌株中亲和分离出一种单一的82 kDa蛋白。与在其他物种中观察到的情况相反，该蛋白与固定化转铁蛋白的结合被牛转铁蛋白的N叶亚片段特异性阻断。编码82 kDa蛋白的单个基因两侧分别是亮氨酰-tRNA合成酶基因和IS1060元件，这与其他物种中编码两种受体蛋白（TbpB和TbpA）的基因以操纵子形式排列不同。尽管观察到所有受体阳性菌株属于不同的基因组群，但在所有这些菌株中都观察到了类似的基因排列。对受体蛋白推导氨基酸序列的分析表明，它是TonB依赖性外膜受体家族的成员，虽然它与其他物种的转铁蛋白和乳铁蛋白受体蛋白（TbpAs和LbpAs）相关，但与该组的其他成员有很大不同。氨基酸比对表明，多杀性巴氏杆菌TbpA尺寸减小（小20 kDa）主要是由于预测的较大外部环缺失。这些结果共同表明，多杀性巴氏杆菌具有一种单一的新型受体蛋白（TbpA），它能够在不涉及第二种受体蛋白（TbpB）的情况下有效地介导从牛转铁蛋白中获取铁。
