Microbial Physiology notes lec19 11-8-10

Microbial Physiology notes lec19 11-8-10 - Microbial Physio...

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Microbial Physio Lecture 19: Chemical Machines in Biology November 8, 2010 -talked about the photosynthetic systems in 5 bacterial phyla, but the complete chart is on lecture 18 November 5, 2010 The Family of “Somes” 1. Cellulosomes: Fxn is to break down cellulose a. Cellulosomes have a basal protein which is called Scaffoldin i. Scaffoldin is a giant protein it has over 2000 amino acids, its one of the very largest proteins ( eukaryotes make proteins that are much larger) ii. Scaffoldin is a 9 cohesin domain repeat protein that binds 9 dockerins ( Ca++ dependent), and the scaffoldin contains cellulose binding domains for binding crystalline cellulose, and at the end by the C-terminus of the scaffoldin is the Double Dockerin domain 1. cohesin is the main structural component of the scaffoldin protein 2. Dockerin domain is a protein domain that is found on the cellulosome cellular structure 3. the dockerin domain binding partner is the cohesin domain their interaction is essential to the construction of the cellulosome complex ( Scaffoldin complex) 4. some Scaffoldin have a quadruplicated “surface layer homologous” (SLH) domain for binding to the cell surface a. this is what the double dockerin domain does, some have a much more complicated structure 5. Scaffoldin protein fxn is to attach to the cellulose via the cellulose binding domain, and also hold onto the catalytic enzymes to break down the cellulose iii. Why is it that eukaryotes would put an entire pathway of gene expression into a single polypeptide chain that was encoded by a single gene, when bacteria would use a distinct enzyme(protein) for each step? 1. the basic difference between a prokaryotic and eukaryotic cell is that a eukaryotic cell is 1000x’s bigger than a prokaryotic cell so in a bacteria, if it makes a bunch of
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proteins that serve a single fxn—that is fatty acid biosynthesis then its not going to be very hard for these proteins to find each other and form a complex 2. on the other hand, the eukaryotic cell is 1000x’s bigger and there are a bunch of compartments in the eukaryotic cell the mitochondrion, peroxisomes, lysosomes, ER, golgi so me proteins and some complexes have to go to one site or to another, and if they were to be scattered around in different compartments it would be a disaster because then wouldn’t have a fully functioning pathway in any one of them, and so to facilitate this and ensure that the entire pathway is present in 1 place/1 organelle, you have 1 gene that encodes for all of them in a eukaryotic cell
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Microbial Physiology notes lec19 11-8-10 - Microbial Physio...

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