Abstract
腎小管間質炎(Tubulointerstitial nephritis)是鉤端螺旋體病(leptospirasis)的主要腎臟表現。LipL32位於致病性鉤端螺旋體的外膜上，是一個重要的致病因子以及主要的脂蛋白。它藉由辨認和附著宿主細胞的細胞外間質成分來迴避免疫反應。我們解出與鈣離子結合的LipL32的晶體結構而且其解析度達 2.3埃。LipL32有一個獨特的polyD序列，由七個天冬胺酸殘基序列所構成，在LipL32結構的表面上形成了一個連續酸性的區域而能與鈣離子結合。鈣離子與LipL32結合產生重要的構形變化。利用等溫滴定量熱儀(Isothermal Titration Calorimeter)偵測出鈣離子與LipL32的結合親和力。利用圓二色光譜儀(Circular Dichroism)以及酵素免疫分析法(ELISA)測出纖維連接蛋白與LipL32的結合力。LipL32與纖維連接蛋白之間的相互作用可能與鈣離子結合有關。根據鈣離子結合的LipL32晶體結構以及功能實驗分析，纖維連接蛋白可能的結合區靠近polyD序列。因此鈣離子可能是鉤端螺旋體和宿主細胞的細胞外間質之相互作用的一個重要因子。 Tubulointerstitial nephritis is a cardinal renal manifestation of leptospirosis. LipL32, a major lipoprotein and a virulence factor, locates on the outer membrane of the pathogen Leptospira. It evades immune response by recognizing and adhering to extracellular matrix components of the host cell. The crystal structure of the Ca2+-bound LipL32 was determined at 2.3 A resolution. LipL32 has a novel polyD sequence of seven aspartate residues that forms a continuous acidic surface patch for Ca2+ binding. A significant conformational change was observed for the Ca2+ bound form of LipL32. The calcium binding to LipL32 was determined by ITC. The binding of fibronectin to LipL32 was observed by Stains-all circular dichroism and ELISA experiments. The interaction between LipL32 and fibronectin might be associated with Ca2+ binding. Based on the crystal structure of the Ca2+-bound LipL32 and the Stains-all results, fibronectin probably binds near to the polyD region on LipL32. The Ca2+ binding to LipL32 might be important for Leptospira to interact with the extracellular matrix interaction of the host cell.