Robert Kranz

Robert Kranz

​Professor of Biology
research interests:
  • Cytochrome Biogenesis
  • Bioenergetics
  • Protein Post-Translational Modification
  • Heme Synthesis, Modification, and Transport

contact info:

mailing address:

  • Washington University
    CB 1137
    One Brookings Drive
    St. Louis, MO 63130-4899

​Since 1987, Professor Kranz's group has studied the molecular mechanisms by which the three pathways (systems I, II, III) covalently attach heme to the protein (apocytochrome c).

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.

recent courses

Laboratory on DNA Manipulation

This course provides investigation-driven research on experimental manipulation of DNA and RNA molecules. This includes the construction, isolation and analysis of plasmids, RNA, PCR products and DNA sequencing. Molecular cloning (genetic engineering), gene knockouts (mutants), RNA isolation, RT-PCR, and microarray projects are performed. Prerequisite: Bio 2960 and Bio 2970. One hour of lecture and six hours of laboratory each week. This course fulfills the upper-level laboratory requirement for the Biology major. Enrollment is limited to 12. A laboratory fee is required for students who are not full-time Washington University undergraduates.

    Selected Publications

    Molecular Basis Behind Inability of Mitochondrial Holocytochrome c Synthase to Mature Bacterial Cytochromes: Defining a Critical Role for Cytochrome c Alpha Helix-1.  Babbitt SE, Hsu J, Kranz RG. J Biol Chem. 2016 Jul 6. 

    Heme Trafficking and Modifications during System I Cytochrome c Biogenesis: Insights from Heme Redox Potentials of Ccm Proteins. Sutherland MC, Rankin JA, Kranz RG. Biochemistry. 2016 Jun 7;55(22):3150-6. 

    Mitochondrial cytochrome c biogenesis: no longer an enigma.  Babbitt SE, Sutherland MC, San Francisco B, Mendez DL, Kranz RG. Trends Biochem Sci. 2015 Aug;40(8):446-55. Review.

    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.