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Nature：細(xì)胞酶研究將導(dǎo)致更好的心臟病和中風(fēng)**
來源:科學(xué)網(wǎng)
   
Nature：細(xì)胞酶研究將導(dǎo)致更好的心臟病和中風(fēng)**加拿大女王大學(xué)的研究揭示了人體內(nèi)一種細(xì)胞酶對心臟病發(fā)作和中風(fēng)之后組織損壞的影響。這一發(fā)現(xiàn)將有助于開發(fā)新的**療法，幫助心臟病發(fā)作和中風(fēng)后恢復(fù)，同時可減少阿爾茨海默氏癥和其他神經(jīng)變性**的影響。相關(guān)論文在線發(fā)表于11月20日的《自然》（Nature）雜志。
    實驗小組由加拿大蛋白質(zhì)工程教授PeterDavies領(lǐng)導(dǎo)，他表示：“這真是令人激動，因為這種蛋白質(zhì)的結(jié)構(gòu)，以及它的抑制劑如何在不損害自身的前提下阻止其活性，一直以來都難以捉摸?！?br>   在細(xì)胞生長和運(yùn)動所需的重塑蛋白中，人體細(xì)胞使用鈣蛋白酶(Calpain)來幫助其與其他蛋白質(zhì)分離。鈣離子濃度的異常增高可激活鈣蛋白酶。而在心臟病發(fā)作和中風(fēng)時，細(xì)胞的血液供應(yīng)中斷，當(dāng)再度供血時，大量涌入的血液使得細(xì)胞內(nèi)鈣離子達(dá)到危險的濃度，使鈣蛋白酶活性增強(qiáng)，結(jié)果給組織造成了很大傷害。研究小組成員RobCampbell表示：“人們不希望酶的激活或關(guān)閉完全不受控制?！?br>   研究還顯示了當(dāng)鈣蛋白酶被鈣離子激活后，另一種蛋白質(zhì)——鈣蛋白酶抑制蛋白（calpastatin）如何阻止了鈣蛋白酶的活性。Campbell和博士生RachelHanna能夠確定鈣綁定的鈣蛋白酶的結(jié)構(gòu)，并發(fā)現(xiàn)了鈣蛋白酶抑制蛋白如何在不受破壞的同時抑制鈣蛋白酶。這將有助于設(shè)計新**，防止過度激活的鈣蛋白酶對組織造成破壞。（創(chuàng)賽新聞中心canspecsci.com）

創(chuàng)賽推薦原始出處：

Nature，456, 409-412，Rachel A. Hanna，Peter L. Davies
Calcium-bound structure of calpain and its mechanism of inhibitionby calpastatin
Rachel A. Hanna1, Robert L. Campbell1 & Peter L. Davies1
    1 Department of Biochemistry, Queen'sUniversity, Kingston, Ontario, Canada K7L 3N6
Calpains are non-lysosomal calcium-dependent cysteine proteinasesthat selectively cleave proteins in response to calcium signals1and thereby control cellular functions such as cytoskeletalremodelling, cell cycle progression, gene expression and apoptoticcell death2, 3, 4. In mammals, the two best-characterized membersof the calpain family, calpain 1 and calpain 2 (-calpain andm-calpain, respectively), are ubiquitously expressed. The activityof calpains is tightly controlled by the endogenous inhibitorcalpastatin, which is an intrinsically unstructured protein capableof reversibly binding and inhibiting four molecules of calpain, butonly in the presence of calcium5, 6. To date, the mechanism ofinhibition by calpastatin and the basis for its absolutespecificity have remained speculative7, 8, 9. It was not clear howthis unstructured protein inhibits calpains without being cleaveditself, nor was it known how calcium induced changes thatfacilitated the binding of calpastatin to calpain. Here we reportthe 2.4-?-resolution crystal structure of the calcium-bound calpain2 heterodimer bound by one of the four inhibitory domains ofcalpastatin. Calpastatin is seen to inhibit calpain by occupyingboth sides of the active site cleft. Although the inhibitor passesthrough the active site cleft it escapes cleavage in a novel mannerby looping out and around the active site cysteine. The inhibitorydomain of calpastatin recognizes multiple lower affinity sitespresent only in the calcium-bound form of the enzyme, resulting inan interaction that is tight, specific and calcium dependent. Thiscrystal structure, and that of a related complex10, also reveal theconformational changes that calpain undergoes on binding calcium,which include opening of the active site cleft and movement of thedomains relative to each other to produce a more compactenzyme.
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