Lin Yi-Jan, Dancea Felician, Löhr Frank, Klimmek Oliver, Pfeiffer-Marek Stefania, Nilges Michael, Wienk Hans, Kröger Achim, Rüterjans Heinz
Institute of Biophysical Chemistry, Center for Biomolecular Magnetic Resonance, J. W. Goethe-University, Marie-Curie-Strasse 9, D-60439 Frankfurt am Main, Germany.
Biochemistry. 2004 Feb 17;43(6):1418-24. doi: 10.1021/bi0356597.
The periplasmic polysulfide-sulfur transferase (Sud) protein encoded by Wolinella succinogenes is involved in oxidative phosphorylation with polysulfide-sulfur as a terminal electron acceptor. The polysulfide-sulfur is covalently bound to the catalytic Cys residue of the Sud protein and transferred to the active site of the membranous polysulfide reductase. The solution structure of the homodimeric Sud protein has been determined using heteronuclear multidimensional NMR techniques. The structure is based on NOE-derived distance restraints, backbone hydrogen bonds, and torsion angle restraints as well as residual dipolar coupling restraints for a refinement of the relative orientation of the monomer units. The monomer structure consists of a five-stranded parallel beta-sheet enclosing a hydrophobic core, a two-stranded antiparallel beta-sheet, and six alpha-helices. The dimer fold is stabilized by hydrophobic residues and ion pairs found in the contact area between the two monomers. Similar to rhodanese enzymes, Sud catalyzes the transfer of the polysulfide-sulfur to the artificial acceptor cyanide. Despite their similar functions and active sites, the amino acid sequences and structures of these proteins are quite different.
琥珀酸沃林氏菌（Wolinella succinogenes）编码的周质多硫化物-硫转移酶（Sud）蛋白参与以多硫化物-硫作为末端电子受体的氧化磷酸化过程。多硫化物-硫共价结合到Sud蛋白的催化半胱氨酸残基上，并转移到膜质多硫化物还原酶的活性位点。已使用异核多维核磁共振技术确定了同二聚体Sud蛋白的溶液结构。该结构基于源自核Overhauser效应（NOE）的距离限制、主链氢键、扭转角限制以及用于细化单体单元相对取向的剩余偶极耦合限制。单体结构由一个包围疏水核心的五链平行β折叠、一个双链反平行β折叠和六个α螺旋组成。二聚体折叠通过两个单体之间接触区域中的疏水残基和离子对得以稳定。与硫氰酸酶类似，Sud催化多硫化物-硫向人工受体氰化物的转移。尽管这些蛋白质具有相似的功能和活性位点，但它们的氨基酸序列和结构却有很大差异。
