Washington University in St. Louis
Campus Box 1137
One Brookings Drive
St. Louis, MO 63130-4899
DBBs graduate programs Plant and Microbial Biosciences Program
Molecular Microbiology and Microbial Pathogenesis Program
- Cytochrome biogenesis
- Protein post-translational modification
- Heme synthesis, modification, and transport
A new frontier in bioenergetics concerns the biogenesis of electron transport complexes, including the orchestrated insertion of critical cofactors. Cytochrome c biogenesis has itself become an excellent model for the intracellular transport of the heme cofactor, control of heme red-ox state, and covalent attachment of heme to the apocytochrome (at a conserved CXXCH motif via thioether bonds). Three pathways (called systems I, II, III) are used to assemble c-type cytochromes (see Fig 1). Prokaryotes (and plants) use system I or II, while mitochondria of fungi to humans use system III. We pursue long-standing studies on the discovery and mechanisms of cytochrome c biogenesis. We have engineered each system to function in Escherichia coli, and we have purified all proteins of each system from E. coli membranes, facilitating an understanding of the molecular mechanisms of biogenesis.
Understanding systems I, II, and III at the deep level will enable the discovery of chemicals (antibiotics) that specifically target the bacterial systems, thus impacting infectious diseases like tuberculosis, meningitis, and other respiratory and inflammatory illnesses. The system III mitochondrial pathway (HCCS) is mutated in human microphthalmia with linear skin defects (MLS) so we will further understand the basis for this disease.
Photo caption: Three unique systems have evolved to assemble the c-type cytochromosomes. The assembly proteins for each system are shown. (c-type cytochromes have heme that is covalently linked to two cysteines.)
Mechanisms of mitochondrial holocytochrome c synthase and the key roles played by cysteines and histidine of the heme attachment site, Cys-XX-Cys-His. Babbitt SE, San Francisco B, Mendez DL, Lukat-Rodgers GS, Rodgers KR, Bretsnyder EC, Kranz RG. J Biol Chem. 2014 289(42):28795-807.
Conserved residues of the human mitochondrial holocytochrome c synthase, HCCS, mediate interactions with heme. Babbitt SE, San Francisco B, Bretsnyder EC, Kranz RG. Biochemistry. 2014 53(32):5261-71
Interaction of holoCcmE with CcmF in heme trafficking and cytochrome c biosynthesis. San Francisco B, Kranz RG. J Mol Biol. 2014. 426(3):570-85.
The CcmFH complex is the system I holocytochrome c synthetase: engineering cytochrome c maturation independent of CcmABCDE. San Francisco B, Sutherland MC, Kranz RG. Mol Microbiol. 2014. 91(5):996-1008.
Human mitochondrial holocytochrome c synthase’s heme binding, maturation determinants, and complex formation with cytochrome c. San Francisco, B, Bretsnyder, EC, Kranz, RG, Proc Natl Acad Sci U S A Plus 2013: 110(9): E788-97.
Thiol redox requirements and substrate specificities of recombinant cytochrome c assembly systems II and III. Richard-Fogal CL, San Francisco B, Frawley ER, Kranz RG. Biochim Biophys Acta. Bioenergetics 2012. 1817(6):911-9
Heme ligand identification and redox properties of the cytochrome c synthetase, CcmF. San Francisco B, Bretsnyder EC, Rodgers KR, Kranz RG. Biochemistry. 2011. 50(50):10974-85.
The CcmC:heme:CcmE complex in heme trafficking and cytochrome c biosynthesis. Richard-Fogal C, Kranz RG. 2010. J Mol Biol. 401(3):350-62.
A conserved haem redox and trafficking pathway for cofactor attachment. Richard-Fogal CL, Frawley ER, Bonner ER, Zhu H, San Francisco B, Kranz RG. EMBO J. 2009;28(16):2349-59.
CcsBA is a cytochrome c synthetase that also functions in heme transport. Frawley ER, Kranz RG. Proc Natl Acad Sci U S A. 2009;106(25):10201-6.
Cytochrome c biogenesis: mechanisms for covalent modifications and trafficking of heme and for heme-iron redox control. Kranz RG, Richard-Fogal C, Taylor JS, Frawley ER. Microbiol Mol Biol Rev. 2009;73(3):510-28, [Invited Review].
ABC transporter-mediated release of a haem chaperone allows cytochrome c biogenesis. Feissner RE, Richard-Fogal CL, Frawley ER, Kranz RG. Mol Microbiol. 2006;61(1):219-31.
Recombinant cytochromes c biogenesis systems I and II and analysis of haem delivery pathways in Escherichia coli. Feissner RE, Richard-Fogal CL, Frawley ER, Loughman JA, Earley KW, Kranz RG. Mol Microbiol. 2006;60(3):563-77.