Sauvé Véronique, Bruno Stefano, Berks Ben C, Hemmings Andrew M
Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom.
J Biol Chem. 2007 Aug 10;282(32):23194-204. doi: 10.1074/jbc.M701602200. Epub 2007 May 23.
The bacterial Sox (sulfur oxidizing) system allows the utilization of inorganic sulfur compounds in energy metabolism. Central to this process is the SoxYZ complex that carries the pathway intermediates on a cysteine residue near the C terminus of SoxY. Crystal structures have been determined for Paracoccus pantotrophus SoxYZ with the carrier cysteine in the underivatized state, conjugated to the polysulfide mimic beta-mercaptoethanol, and as the sulfonate adduct pathway intermediate. The carrier cysteine is located on a peptide swinging arm and is bracketed on either side by diglycine dipeptides acting as molecular universal joints. This structure provides a novel solution to the requirement that the cysteine-bound intermediates be able to access and orient themselves within the active sites of multiple partner enzymes. Adjacent to the swinging arm there is a conserved, deep, apolar pocket into which the beta-mercaptoethanol adduct extends. This pocket would be well suited to a role in protecting labile pathway intermediates from adventitious reactions.
细菌的Sox（硫氧化）系统能够在能量代谢过程中利用无机硫化合物。该过程的核心是SoxYZ复合物，它在SoxY C末端附近的一个半胱氨酸残基上携带途径中间体。已确定嗜甲基副球菌SoxYZ的晶体结构，其载体半胱氨酸处于未衍生化状态、与多硫化物模拟物β-巯基乙醇共轭以及作为磺酸盐加合物途径中间体的状态。载体半胱氨酸位于一个肽摆动臂上，两侧由作为分子万向节的二甘氨酸二肽包围。这种结构为半胱氨酸结合的中间体能够在多种伙伴酶的活性位点内接近并自我定向这一要求提供了一种新颖的解决方案。在摆动臂旁边有一个保守的、深的、非极性口袋，β-巯基乙醇加合物延伸到其中。这个口袋非常适合在保护不稳定的途径中间体免受偶然反应方面发挥作用。
