首页 | 本学科首页   官方微博 | 高级检索  
   检索      


Loss of iron-sulfur clusters from biotin synthase as a result of catalysis promotes unfolding and degradation
Authors:Reyda Michael R  Dippold Rachael  Dotson Michael E  Jarrett Joseph T
Institution:a Department of Chemistry, University of Hawaii at Manoa, 2545 McCarthy Mall, Honolulu, HI 96822-2275, United States
b Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA 19104, United States
Abstract:Biotin synthase (BioB) is an S-adenosylmethionine radical enzyme that catalyzes addition of sulfur to dethiobiotin to form the biotin thiophane ring. In vitro, Escherichia coli BioB is active for only one turnover, during which the 2Fe-2S]2+ cluster is destroyed, one sulfide from the cluster is incorporated as the biotin thiophane sulfur, while Fe2+ ions and the remaining S2− ion are released from the protein. The present work examines the fate of the protein following the loss of the FeS clusters. We examine the quaternary structure and thermal stability of active and inactive states of BioB, and find that loss of either the 4Fe-4S]2+ or 2Fe-2S]2+ clusters results in destabilization but not global unfolding of BioB. Using susceptibility to limited proteolysis as a guide, we find that specific regions of the protein appear to be transiently unfolded following loss of these clusters. We also examine the in vivo degradation of biotin synthase during growth in low-iron minimal media and find that BioB is degraded by an apparent ATP-dependent proteolysis mechanism that sequentially cleaves small fragments starting at the C-terminus. BioB appears to be resistant to degradation and capable of multiple turnovers only under high-iron conditions that favor repair of the FeS clusters, a process most likely mediated by the Isc or Suf iron-sulfur cluster assembly systems.
Keywords:Biotin synthase  BioB  Iron-sulfur cluster  Protein degradation
本文献已被 ScienceDirect PubMed 等数据库收录!
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号