A Minimum of Three Motifs Is Essential for Optimal Binding of Pseudomurein Cell Wall-Binding Domain of Methanothermobacter thermautotrophicus

We have biochemically and functionally characterized the pseudomurein cell wall-binding (PMB) domain that is present at the C-terminus of the Surface (S)-layer protein MTH719 from Methanothermobacter thermautotrophicus. Chemical denaturation of the protein with guanidinium hydrochloride occurred at 3.8 M. A PMB-GFP fusion protein not only binds to intact pseudomurein of methanogenic archaea, but also to spheroplasts of lysozyme-treated bacterial cells. This binding is pH dependent. At least two of the three motifs that are present in the domain are necessary for binding. Limited proteolysis revealed a possible cleavage site in the spacing sequence between motifs 1 and 2 of the PMB domain, indicating that the motif region itself is protected from proteases.

我们对来自嗜热自养甲烷杆菌（Methanothermobacter thermautotrophicus）的表面（S）层蛋白MTH719 C端的假肽聚糖细胞壁结合（PMB）结构域进行了生化与功能表征。该蛋白在3.8 M浓度的盐酸胍（guanidinium hydrochloride）作用下发生化学变性。PMB-GFP融合蛋白不仅可结合产甲烷古菌的完整假肽聚糖，还可结合经溶菌酶处理的细菌细胞的原生质球。该结合过程具有pH依赖性。该结构域所含的三个基序中，至少需具备两个才能实现结合功能。有限蛋白水解实验显示，PMB结构域的基序1与基序2之间的间隔序列中存在潜在切割位点，这表明基序区域本身可免受蛋白酶的降解。