Smalley J W, Birss A J
Department of Clinical Dental Sciences, The University of Liverpool, Liverpool, L69 3BX, U.K.
Microb Pathog. 1999 Mar;26(3):131-7. doi: 10.1006/mpat.1998.0259.
Cells of Porphyromonas gingivalis strains W50 and WPH35 bound albumin and haemalbumin complexes (with 2:1 and 1:1 molar ratios of protein to iron protoporphyrin IX) in a concentration-dependent manner. The binding capacity for both haemalbumins was greater than for albumin. Scatchard analysis of binding to strain W50 revealed monophasic binding for albumin with an association constant (Ka) approximately 10(5)/M. Binding of the haemalbumin complexes was biphasic. The Kas of the lower-affinity binding phases were similar to that for albumin, whilst those for the higher-affinity binding were approximately 20-30-fold greater. It is concluded that both the capacity and avidity for albumin binding to P. gingivalis are increased following haemalbumin complex formation. This phenomenon would enable cells to discriminate between albumin and haem-bearing albumin molecules as a potential source of haem. Such binding behaviour may confer a nutritional and ecological advantage in the periodontal pocket or gingival sulcus under conditions of haem limitation.
牙龈卟啉单胞菌菌株W50和WPH35的细胞以浓度依赖的方式结合白蛋白和血红蛋白复合物（蛋白质与铁原卟啉IX的摩尔比为2:1和1:1）。两种血红蛋白的结合能力均大于白蛋白。对菌株W50结合情况的Scatchard分析显示，白蛋白的结合为单相，缔合常数（Ka）约为10(5)/M。血红蛋白复合物的结合为双相。低亲和力结合阶段的Ka与白蛋白的相似，而高亲和力结合阶段的Ka大约大20 - 30倍。得出的结论是，形成血红蛋白复合物后，白蛋白与牙龈卟啉单胞菌结合的能力和亲和力均增加。这种现象使细胞能够区分白蛋白和携带血红素的白蛋白分子，将其作为血红素的潜在来源。在血红素受限的条件下，这种结合行为可能在牙周袋或牙龈沟中赋予营养和生态优势。
