REPEAT UNIT POLYSACCHARIDES OF BACTERIA - A MODEL FOR POLYMERIZATION RESEMBLING THAT OF RIBOSOMES AND FATTY-ACID SYNTHETASE, WITH A NOVEL MECHANISM FOR DETERMINING CHAIN-LENGTH
REPEAT UNIT POLYSACCHARIDES OF BACTERIA - A MODEL FOR POLYMERIZATION RESEMBLING THAT OF RIBOSOMES AND FATTY-ACID SYNTHETASE, WITH A NOVEL MECHANISM FOR DETERMINING CHAIN-LENGTH
复制标题
DOI：
10.1111/j.1365-2958.1993.tb01163.x
复制
发表时间：
1993-03-01
影响因子：
3.6
通讯作者：
REEVES, PR
中科院分区：
文献类型：
--
作者：
BASTIN, DA;STEVENSON, G;REEVES, PR
我们报告的鉴定和序列从大肠杆菌和沙门氏菌菌株的cld基因，编码的链长度决定簇（CLD），赋予一个模态分布的链长度的0-抗原组分的脂多糖（LPS）。在不存在该基因的情况下，链长的分布符合一个模型，其中随着链的延伸，存在0.165的恒定概率将生长的链转移到LPS核心，并终止链延伸。E.大肠杆菌0111的结果符合一个模型，其中CLD降低了短链的这种概率，并将其增加到0.4，导致短链分子的数量减少，但较长分子的数量增加，并且基本上所有的分子都转移了链长21。我们提出了一个0-抗原聚合酶的模型，它类似于核糖体和脂肪酸合成酶，具有两个位点，生长链从D位点转移到R位点的新单元上以延伸链，然后回到D位点重复该过程。提出CLD蛋白和聚合酶形成具有两种状态的复合物：“E”促进延伸和“T”促进转移到核心。假设复合物在0-抗原聚合开始时进入E状态，并在预定时间后转变为T状态，CLD充当分子钟。CLD不是0抗原或种特异性的，但模态值确实取决于cld基因的来源。
We report the identification and sequence from Escherichia coli and Salmonella enterica strains of the cld gene, encoding the chain-length determinant (CLD) which confers a modal distribution of chain length on the 0-antigen component of lipopolysaccharide (LPS). The distribution of chain lengths in the absence of this gene fits a model in which as the chain is extended there is a constant probability of 0.165 of transfer of growing chain to LPS core, with termination of chain extension. The data for E. coli 0111 fit a model in which the CLD reduces this probability for short chains and increases it to 0.4 for longer chains, leading to a reduced number of short chain molecules but an increase in numbers of longer molecules and transfer of essentially all molecules by chain length 21. We put forward a model for 0-antigen polymerase which resembles the ribosome and fatty acid synthetase in having two sites, with the growing chain being transferred from a D site onto the new unit at the R site to extend the chain and then back to the D site to repeat the process. it is proposed that the CLD protein and polymerase form a complex which has two states: 'E' facilitating extension and 'T' facilitating transfer to core. The complex is postulated to enter the E state as 0-antigen polymerization starts, and to shift to the T state after a predetermined time, the CLD acting as a molecular clock. The CLD is not 0-antigen or species-specific but the modal value does depend on the source of the cld gene.