IDENTIFICATION AND CHARACTERIZATION OF A BACTEROIDES GENE, CSUF, WHICH ENCODES AN OUTER-MEMBRANE PROTEIN THAT IS ESSENTIAL FOR GROWTH ON CHONDROITIN SULFATE
IDENTIFICATION AND CHARACTERIZATION OF A BACTEROIDES GENE, CSUF, WHICH ENCODES AN OUTER-MEMBRANE PROTEIN THAT IS ESSENTIAL FOR GROWTH ON CHONDROITIN SULFATE
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DOI：
10.1128/jb.177.13.3721-3727.1995
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发表时间：
1995-07-01
影响因子：
3.2
通讯作者：
SALYERS, AA
中科院分区：
文献类型：
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作者：
CHENG, QO;YU, MC;SALYERS, AA
多形拟杆菌可以利用多种多糖，包括带电荷的粘多糖，如硫酸软骨素（CS）和透明质酸（HA）。由于催化CS和HA分解第一步的酶（软骨素裂解酶I和II）位于周质中，我们提出利用这些多糖的第一步是结合一个或多个外膜蛋白，然后易位到周质中，但没有这样的外膜蛋白已被证明在CS或HA利用中发挥作用。以前，我们已经分离出一个转座子产生的突变体，CS4，这是不能生长的CS或HA，但保留了能力，CS的二糖成分上生长。这种表型表明CS4中的突变要么阻断粘多糖转运到周质空间，要么阻断粘多糖解聚成二糖。我们已经将CS4突变定位到单个基因csuF上，该基因能够编码1，065个氨基酸的蛋白质，并含有一个共有信号序列。虽然CsuF具有与软骨素裂解酶相似的预测分子量和pI，但它与拟杆菌软骨素裂解酶II、变形杆菌软骨素ABC裂解酶或产气荚膜梭菌和化脓性链球菌的两种透明质酸酶没有显示出显著的序列相似性，也没有任何CS降解酶活性与拟杆菌属物种或大肠杆菌中的csuF表达相关。推导的氨基酸序列的CsuF表现出的功能暗示的外膜蛋白。我们获得了CsuF的抗体，并证明该蛋白质位于外膜。这是第一个证据表明，非酶外膜蛋白是必不可少的利用CS和HA。
Bacteroides thetaiotaomicron can utilize a variety of polysaccharides, including charged mucopolysaccharides such as chondroitin sulfate (CS) and hyaluronic acid (HA). Since the enzymes (chondroitin lyases I and II) that catalyze the first step in breakdown of CS and HA are located in the periplasm, we had proposed that the first step in utilization of these polysaccharides was binding to one or more outer membrane proteins followed by translocation into the periplasm, but no such outer membrane proteins had been shown to play a role in CS or HA utilization. Previously we had isolated a transposon-generated mutant, CS4, which was unable to grow an CS or HA but retained the ability to grow on disaccharide components of CS. This phenotype suggested that the mutation in CS4 either blocked the transport of the mucopolysaccharides into the periplasmic space or blocked the depolymerization of the mucopolysaccharides into disaccharides. We have mapped the CS4 mutation to a single gene, csuF, which is capable of encoding a protein of 1,065 amino acids and contains a consensus signal sequence. Although CsuF had a predicted molecular weight and pI similar to those of chondroitin lyases, it did not show significant sequence similarity to the Bacteroides chondroitin lyase II, a Proteus chondroitin ABC lyase, or two hyaluronidases from Clostridium perfringens and Streptococcus pyogenes, nor was any CS-degrading enzyme activity associated with csuF expression in Bacteroides species or Escherichia coli. The deduced amino acid sequence of CsuF exhibited features suggestive of an outer membrane protein. We obtained antibodies to CsuF and demonstrated that the protein is located in the outer membrane. This is the first evidence that a nonenzymatic outer membrane protein is essential for utilization of CS and HA.