2012年9月21日 訊 /生物谷BIOON/ --在一項(xiàng)于近期在線刊登在PNAS期刊上的新研究中,，一個(gè)研究小組利用來(lái)自斯坦福同步輻射實(shí)驗(yàn)室(Stanford Synchrotron Radiation Laboratory, SSRL)的明亮X射線解析出一種酶復(fù)合體的晶體結(jié)構(gòu)。在此之前，科學(xué)家們花了將近10年的時(shí)間來(lái)試圖解析它的結(jié)構(gòu),，但是都沒(méi)獲得成功。他們的這項(xiàng)研究可能導(dǎo)致人們?cè)谖磥?lái)開(kāi)發(fā)出抗菌試劑來(lái)抵抗一系列致命性細(xì)菌,，包括炭疽菌,、結(jié)核分枝桿菌、麻風(fēng)桿菌和白喉?xiàng)U菌。
這些細(xì)菌利用這種被稱作黃素依賴性胸苷酸合酶(flavin-dependent thymidylate synthase, FDTS)來(lái)合成一種他們用于合成DNA的核苷酸,。其他的有機(jī)體(包括人)依賴于一種不同類型的酶來(lái)完成這種關(guān)鍵性過(guò)程,。這兩種不同類型的酶之間的差異非常顯著以致于通過(guò)藥物療法靶向細(xì)菌FDTS應(yīng)當(dāng)不會(huì)干擾人體內(nèi)相應(yīng)酶的功能。換句話說(shuō),，靶向細(xì)菌FDTS的藥物導(dǎo)致人產(chǎn)生副作用的可能性比較低,。
根據(jù)論文通信作者Irimpan Mathews的說(shuō)法，解析酶FDTS結(jié)構(gòu)的苦難在于獲得這種酶的晶體以便準(zhǔn)確地揭示藥物需要靶向它的哪一部分,。
研究人員一直試圖分離出來(lái)的靶標(biāo)是在核苷酸合成期間FDTS與化合物亞甲基四氫葉酸(methylenetetrahydrofolate)結(jié)合的位點(diǎn),。Mathews說(shuō)，“沒(méi)有人能夠獲得與這種化合物或類似化合物結(jié)合的FDTS結(jié)構(gòu),。”
培養(yǎng)晶體方法上的進(jìn)步,，再結(jié)合來(lái)自SSRL光束線9-2和12-2的X射線，才讓研究人員首次成功地解析出FDTS與亞甲基四氫葉酸或它的類似物結(jié)合時(shí)的結(jié)構(gòu),。
Mathews認(rèn)為,，這項(xiàng)研究發(fā)現(xiàn)有助于人們發(fā)現(xiàn)一種新的方法來(lái)設(shè)計(jì)抑制一系列有害菌的藥物。(生物谷Bioon.com)
doi: 10.1073/pnas.1206077109
PMC:
PMID:
Folate binding site of flavin-dependent thymidylate synthase
Eric M. Koehna, Laura L. Perissinottia, Salah Moghrama, Arjun Prabhakarb, Scott A. Lesleyc, Irimpan I. Mathewsb,1, and Amnon Kohen
The DNA nucleotide thymidylate is synthesized by the enzyme thymidylate synthase, which catalyzes the reductive methylation of deoxyuridylate using the cofactor methylene-tetrahydrofolate (CH2H4folate). Most organisms, including humans, rely on the thyA- or TYMS-encoded classic thymidylate synthase, whereas, certain microorganisms, including all Rickettsia and other pathogens, use an alternative thyX-encoded flavin-dependent thymidylate synthase (FDTS). Although several crystal structures of FDTSs have been reported, the absence of a structure with folates limits understanding of the molecular mechanism and the scope of drug design for these enzymes. Here we present X-ray crystal structures of FDTS with several folate derivatives, which together with mutagenesis, kinetic analysis, and computer modeling shed light on the cofactor binding and function. The unique structural data will likely facilitate further elucidation of FDTSs’ mechanism and the design of structure-based inhibitors as potential leads to new antimicrobial drugs.
