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closeSuper cytochromes?
Posted by nswigginton on 08 May 2008 at 02:59 GMT
Just a few hypothetical questions: What could a 40-heme cytochrome possibly look like? How is its physiological role different from, say, an octaheme cytochrome? It's fascinating to think that we still really don't understand this whole electron transfer/respiration thing. Papers like this are excellent at framing these questions in a broad biological context, but I hope they also encourage others to try and figure out the physics/chemistry behind such interesting proteins. Maybe a 40-heme cytochrome would perform well in a biofuel cell? Maybe it'll tell us about the evolution of such sophisticated cellular machinery?
RE: Super cytochromes?
shthomas replied to nswigginton on 08 May 2008 at 20:34 GMT
Dr. Wiggington asks an intriguing question: What is the physiological function of c-type cytochromes with so many heme-binding motifs? We don’t know at this point but from the response we received it is obvious that a larger group of researchers is interested in addressing this question.
Genes with many heme-binding sites appear common among Anaeromyxobacter spp. The genome of strain FW109-5 contains three genes with even greater numbers of putative heme-binding motifs (45, 51, and 58). Of course, we don’t know if these putative heme-binding sites are all occupied by heme groups in the functional protein. In any case, large numbers of c-type cytochromes with multiple heme-binding motifs are common in bacteria displaying respiratory versatility (e.g., Shewanella. Geobacter, Anaeromyxobacter). A few of these c-type cytochromes have been studied in more detail but we have yet to understand the complexity and the in vivo interactions and function(s). In a recent paper, Esteve-Núñez et al. (Environmental Microbiology, 2008, 10:497-505) suggest that c-type cytochromes might act as capacitors to fuel the cell’s energy metabolism during famine conditions. Hopefully, combined isolation, genome mining, and biochemical and physical characterization efforts will elucidate the nature of these intriguing proteins.