Department of Chemistry and Biochemistry, University of Bern, Bern, Switzerland.
PLoS One. 2012;7(8):e43863. doi: 10.1371/journal.pone.0043863. Epub 2012 Aug 24.
Archaemetzincins are metalloproteases occurring in archaea and some mammalia. They are distinct from all the other metzincins by their extended active site consensus sequence HEXXHXXGXXHCX(4)CXMX(17)CXXC featuring four conserved cysteine residues. Very little is known about their biological importance and structure-function relationships.
Here we present three crystal structures of the archaemetzincin AfAmzA (Uniprot O29917) from Archaeoglobus fulgidus, revealing a metzincin architecture featuring a zinc finger-like structural element involving the conserved cysteines of the consensus motif. The active sites in all three structures are occluded to different extents rendering the enzymes proteolytically inactive against a large variety of tested substrates. Owing to the different ligand binding there are significant differences in active site architecture, revealing a large flexibility of the loops covering the active site cleft.
The crystal structures of AfAmzA provide the structural basis for the lack of activity in standard proteolytic assays and imply a triggered activity onset upon opening of the active site cleft.
古菌金属蛋白酶是在古菌和一些哺乳动物中存在的金属蛋白酶。它们与所有其他的金属蛋白酶不同，其延伸的活性位点共识序列 HEXXHXXGXXHCX(4)CXMX(17)CXXC 具有四个保守的半胱氨酸残基。关于它们的生物学重要性和结构-功能关系，我们知之甚少。
在这里，我们展示了来自产甲烷古菌（ Archaeoglobus fulgidus ）的古菌金属蛋白酶 AfAmzA（ Uniprot O29917 ）的三个晶体结构，揭示了一种金属蛋白酶结构，其特征是具有锌指样结构元件，涉及共识基序的保守半胱氨酸。所有三个结构的活性部位都不同程度地被阻塞，使酶对大量测试的底物表现出无蛋白水解活性。由于配体结合的不同，活性部位结构有很大的差异，揭示了覆盖活性部位裂缝的环的很大的灵活性。
AfAmzA 的晶体结构为标准蛋白水解测定中缺乏活性提供了结构基础，并暗示活性部位裂缝打开时活性的触发。
