Structure, function and biogenesis of proteins catalysing respiratory and transport processes in the N-cycle
Co-workers: Dr Shilpa Bali, Dr Despoina Mavridou, Dr Julie Stevens, Shevket Halil Shevket, Yulin Zhang
Bacterial respiratory pathways are diverse and complex and include cytochromes c and a variety of metalloenzymes. Our work aims to understand the assembly of these cofactor-containing proteins and how they function. In collaboration with colleagues in Molecular Biophysics we obtained the crystal structure of the bacterial respiratory enzyme nitrite reductase. This enzyme is involved in the nitrogen cycle in the process of denitrification, which, if occurring at nadequate rates will have adverse effects on the environment (eg. high levels of nitrate in soil or release of nitrous oxide into the atmosphere). A major group of respiratory proteins, the c-type cytochromes, contain covalently linked heme groups. The attachment of the heme to the protein is complex and involves many proteins, including ransmembrane transport proteins and proteins that function in disulphide bond isomerisation.
Proteins involved in disulphide bond formation are of particular significance because many extracellular bacterial toxins contain disulphide bonds and it is therefore important to understand the mechanisms by which these bonds form. In Gram-negative bacteria the protein and the heme cofactor must be transported to the periplasm for the c-type cytochrome assembly process. It is not known how the heme is transported across the membrane or how it becomes attached to the cytochrome polypeptide. Another perplexing transport event in the N-cycle is how nitrate and nitrite used in respiration respectively enter and exit the cell. We employ an array of methodologies to study the respiratory proteins and the processes involved in their assembly.
Publications1 Bali S, Rollauer S, Roversi P, Raux-Deery E, Lea SM, Warren MJ, Ferguson SJ. (2014) Identification and characterization of the 'missing' terminal enzyme for siroheme biosynthesis in α-proteobacteria. Mol Microbiol 92(1):153-63.
2 Bali S, Palmer DJ, Schroeder S, Ferguson SJ, Warren MJ. (2014) Recent advances in the biosynthesis of modified tetrapyrroles: the discovery of an alternative pathway for the formation of heme and heme d1. Cell Mol Life Sci 71(15):2837-63.
3 Mavridou DA, Saridakis E, Kritsiligkou P, Mozley EC, Ferguson SJ, Redfield C. (2014) An extended active-site motif controls the reactivity of the thioredoxin fold. J Biol Chem. 289(12):8681-96.
4 Luque-Almagro VM, Lyall VJ, Ferguson SJ, Roldán MD, Richardson DJ, Gates AJ. (2013) Nitrogen oxyanion-dependent dissociation of a two-component complex that regulates bacterial nitrate assimilation. J Biol Chem 288(41):29692-702.
5 Mavridou DA, Ferguson SJ, Stevens JM (2013) Cytochrome c assembly. IUBMB Life 65(3):209-16.
6 Mavridou DA, Stevens JM, Mönkemeyer L, Daltrop O, di Gleria K, Kessler BM, Ferguson SJ, Allen JW. (2012) A pivotal heme-transfer reaction intermediate in cytochrome c biogenesis. J Biol Chem. 287(4):2342-52.
7 Bali S, Lawrence AD, Lobo SA, Saraiva LM, Golding BT, Palmer DJ, Howard MJ, Ferguson SJ, Warren MJ (2011) Molecular hijacking of siroheme for the synthesis of heme and d1 heme. Proc Natl Acad Sci USA 108(45):18260-5.
8 Mavridou DA, Saridakis E, Kritsiligkou P, Goddard AD, Stevens JM, Ferguson SJ, Redfield C.(2011) Oxidation state-dependent protein-protein interactions in disulfide cascades. J Biol Chem 286(28):24943-56.
9 Harvat EM, Redfield C, Stevens JM and Ferguson SJ (2009) Probing the heme-binding site of the cytochrome c maturation protein CcmE. Biochemistry 48, 1820-1828
10 Goddard AD, Moir JWB, Richardson DJ and Ferguson SJ (2008) Interdependence of two Nark domains in a fused nitrate/nitrite transporter. Mol Microbiol 70, 667-681
11 Sam KA, Strampraad MJF, de Vries S, and Ferguson SJ (2008) Very early reaction intermediates detected by microsecond time scale kinetics of cytochrome cd1-catalyzed reduction of nitrite. J Biol Chem 283, 27403-27409
Figure 1: Cytochrome cd1 nitrite reductase
Figure 2: The Nitrogen Cycle
Figure 3: NMR studies of cDsbD (with Dr Christina Redfield - Cover figure on the 20 July 2007 issue of the Journal of Molecular Biology)
Figure 4: Illustrating the main components of cytochrome c biogenesis Systems I (top) and I* (bottom). The representations of Systems I and I* are based on the model organisms E. coli and D. alaskensis, respectively
Figure 5: Redox potentiometry of a heme-containing protein