Hell Wolfgang, Reichl Sylvia, Anders Agnes, Gatermann Sören
Institute of Medical Microbiology, Ruhr Universität Bochum, D-44780, Bochum, Germany.
FEMS Microbiol Lett. 2003 Oct 10;227(1):47-51. doi: 10.1016/S0378-1097(03)00647-5.
The Aas (autolysin/adhesin of Staphylococcus saprophyticus) is a multifunctional surface protein containing two enzymatic domains an N-acetyl-muramyl-L-alanine amidase, an endo-beta-N-acetyl-D-glucosaminidase, and two different regions of repetitive sequences, an N-terminal and a C-terminal repetitive domain. The C-terminal repetitive domain is built up by the repeats R1, R2 and R3, which interconnect the putative active centers of the amidase and glucosaminidase. To investigate the influence of the C-terminal repeats and the N-terminal repeats on the amidase activity, the repetitive domains and fragments of them were cloned and expressed in Escherichia coli. The influence of the different fragments on the activity of the recombinant amidase of the Aas, consisting of the active center of the enzyme and repeat R1, was investigated in a turbidimetric microassay. The different fragments derived from the C-terminal repeats inhibited the amidase activity, while the N-terminal repeats did not influence the activity of the enzyme. The inhibiting activity increased with the number of GW repeats the recombinant fragment contained. Thus we conclude, that the C-terminal GW repeats and not the N-terminal repeats are necessary for the cell wall targeting and the autolytic function of the amidase.
腐生葡萄球菌自溶素/黏附素（Aas）是一种多功能表面蛋白，包含两个酶结构域，即N - 乙酰胞壁酰 - L - 丙氨酸酰胺酶、内切β - N - 乙酰 - D - 葡萄糖胺酶，以及两个不同的重复序列区域，即N端和C端重复结构域。C端重复结构域由R1、R2和R3重复序列组成，它们将酰胺酶和葡萄糖胺酶的假定活性中心相互连接。为了研究C端重复序列和N端重复序列对酰胺酶活性的影响，将这些重复结构域及其片段进行克隆并在大肠杆菌中表达。在比浊法微量测定中，研究了不同片段对由酶活性中心和重复序列R1组成的Aas重组酰胺酶活性的影响。来自C端重复序列的不同片段抑制了酰胺酶活性，而N端重复序列对酶活性没有影响。抑制活性随着重组片段所含GW重复序列数量的增加而增强。因此我们得出结论，C端GW重复序列而非N端重复序列对于酰胺酶的细胞壁靶向作用和自溶功能是必需的。
