Amend A, Chhatwal G S, Schaeg W, Blobel H
Zentralbl Bakteriol Mikrobiol Hyg A. 1984 Dec;258(4):472-9. doi: 10.1016/s0176-6724(84)80024-3.
Protein A (PA)-activity was detected in Staphylococcus aureus strain Wood 46 which had been considered to be PA-negative. This staphylococcal strain bound 28% of 125I-labelled IgG, compared with 89% by strain Cowan I. The binding activities of both S. aureus strains were saturable, time-dependent and specific. The dissociation constants of 1.6 X 10(-9) M for Wood 46 and 9.3 X 10(-8) M for Cowan I indicated a similar affinity for human IgG in both strains. The number of IgG-binding sites were estimated to be 16,970 for Wood 46 and 41,200 for Cowan I. Exposure to heat and ultrasonication reduced PA-activities of strain Cowan I, but not that of strain Wood 46. Extraction of the staphylococci with guanidine and formic acid resulted in a reduction of IgG-binding activities only in strain Wood 46. Photooxidation, trypsinization and lysozyme treatment also diminished IgG-binding of strain Wood 46 to a larger extent than that of strain Cowan I. Extracellular PA from S. aureus strains Wood 46 and Cowan I could be purified by affinity chromatography on IgG-sepharose. The purified PA preparations gave single protein bands upon SDS-polyacrylamide gel electrophoresis. Their molecular weights were 42,000 and their isoelectric points approximated 5.0.
在曾被认为蛋白A（PA）呈阴性的金黄色葡萄球菌伍德46菌株中检测到了PA活性。该葡萄球菌菌株结合了28%的125I标记的IgG，而考恩I菌株的结合率为89%。两种金黄色葡萄球菌菌株的结合活性都是可饱和的、时间依赖性的且具有特异性。伍德46菌株的解离常数为1.6×10（-9）M，考恩I菌株的解离常数为9.3×10（-8）M，这表明两种菌株对人IgG的亲和力相似。伍德46菌株的IgG结合位点数量估计为16,970个，考恩I菌株为41,200个。加热和超声处理降低了考恩I菌株的PA活性，但未降低伍德46菌株的PA活性。用胍和甲酸提取葡萄球菌仅导致伍德46菌株的IgG结合活性降低。光氧化、胰蛋白酶处理和溶菌酶处理也使伍德46菌株的IgG结合能力比考恩I菌株下降得更明显。来自金黄色葡萄球菌伍德46菌株和考恩I菌株的细胞外PA可通过IgG-琼脂糖亲和层析进行纯化。纯化后的PA制剂在SDS-聚丙烯酰胺凝胶电泳上呈现单一蛋白条带。它们的分子量为42,000，等电点约为5.0。
