Structural analysis of adenylate cyclases from Trypanosoma brucei in their monomeric state
Structural analysis of adenylate cyclases from Trypanosoma brucei in their monomeric state
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DOI：
10.1093/emboj/20.3.433
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发表时间：
2001-02-01
期刊：
影响因子：
11.4
通讯作者：
Essen, LO
中科院分区：
文献类型：
--
作者：
Bieger, B;Essen, LO
环磷酸腺苷是引起昏睡病的血液寄生虫布鲁氏锥虫分化过程的主要触发因素。它在锥体中的产生是由一组独特的膜结合的腺苷环化酶(ACS)完成的。我们测定了两个锥体ACS(Tacs)GRESAGL4.1和GRESAG4.3催化结构域的高分辨X射线结构。TAC结构域在结构上与高等真核生物的AC结构域高度相关，但也包括活性部位附近的高度保守的结构元件-Delta亚域。Delta亚区下方的空腔可能对应于一个变构调节部位，这表明单一的(2S，3S)-1，4-二巯基-2，3-丁二醇分子具有立体特异性结合。在三种不同的晶体形式中，TAC结构域仅以单体的催化非活性状态观察到。生化分析和GRESAG4.1的诱变图谱证实了Tacs的一个共同的催化机制，即AC结构域的瞬时二聚。如果Tacs的激活类似于膜结合的鸟苷环化酶一样，由配体诱导的二聚化驱动，则低二聚化趋势可能在布鲁氏毛滴虫中起到调节作用。
Cyclic AMP is a major trigger of the differentiation process of Trypanosoma brucei, a bloodstream parasite causing sleeping sickness. Its generation in trypanosomes is accomplished by a unique battery of membrane-bound adenylate cyclases (ACs). We have determined the high-resolution X-ray structures of the catalytic domains of two trypanosomal ACs (tACs), GRESAGL4.1 and GRESAG4.3. The tAC domains are structurally highly related to the AC domains of higher eukaryotes, but also comprise a highly conserved structural element near the active site, the Delta -subdomain. A cavity below the Delta -subdomain might correspond to an allosteric regulator site as indicated by the stereospecific binding of a single (2S,3S)-1,4-dimercapto-2,3-butanediol molecule. In three different crystal forms, the tAC domains are exclusively observed in a monomeric, catalytically inactive state. Biochemical analysis and the mutagenesis profile of GRESAG4.1 confirmed a common catalytic mechanism of tACs that involves transient dimerization of the AC domain. A low dimerization tendency might play a regulatory role in T.brucei if the activation of tACs is similarly driven by ligand-induced dimerization as in membrane-bound guanylate cyclases.