mistral92
Forum Senior
Topics: 4
Posts: 185
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what does ADP ribosylation means???
what is the role or function of adenylate cyclase???
guanylate cyclase???
what 's coagulase ( staph) means???
what is Gs ....Gm??? ( cholera and diphteria)
do you a mneumonic for oxidase and urease bacteria???
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| meg
Forum Guru
Topics: 62
Posts: 806
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1 and 2)There are ADP ribosyltransferases in cells which bind NAD to from Nicotinamide and ADP. This ADP gets bound to aminoacid on target molecules and brings about an effect. For example, in cholera and E.Coli LT, they cause the attachment of ADP to Arginine residue on Adenylate cyclase. This triggers it on to form more cAMP and the cascade begins. So it is basically adding ADP(which is a ribose nucleotide) to an aminoacid in a target molecule. This is caused by Diph, pseudomonas, pertussis, vib cholera, and Ecoli (heat Labile Toxin).
3)Guanylate cyclase converts GTP to cGMP. This is effected in E.Coli ST(stable toxin). This is the cascade used by nitrates, Atrial natriuretic peptide and NO.
4) Coagulase is an enzyme that coagulates proteins(makes clumps by distorting their secondary structure - denaturation). Staph aureus (not epidermis /saprophyticus) produces this and basically it is the way it walls off itself from being attacked by immune cells. Also this is why you get localised lesions, unlike Strep which produces hyaluronidase which breaks down ground substance barriers and spreads all over body.
5)In our cells, there are serpentine receptors(traverse seven times) and these are attached to proteins called G proteins which have 3 subunits (alpha, beta, gamma). When there is no ligand attached to the serpentine receptor, the alpha subunit binds to GDP. If receptor binds to ligand, GTP becomes GDP and alpha dissociates from beta and gamma and then stimulates the next mediator. Now, this mediator can be adenylate cyclase, guanylate cyclase, or phospholipase C. If the binding of alpha unit to adenylate cyclase stimulates adenylate cylcase to convert ATP to cAMP then the G protein is a Gs, else if it inhibits adenylate cyclase, then it is a Gi. If it works by Phospholipase C, then it is a Gq. There is also a Gt which stimulates transducin in the retina (rods and cones).
Gs = beta adrenergic, M1 and M3,vibrio cholera, almost all other than those on Gq
Gi= pertussis
Gq= alpha1 , Vasopressin 1, Angiotensin II, Oxytocin, M2 heart
Oxidase I am not sure, but for UREASE it is
PUNCH
Proteus, Urease, Nocardia, Cryptococcus, Helicobacter
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| mistral92
Forum Senior
Topics: 4
Posts: 185
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hello meg!!!! i'd like to thank you for your explanations!!!! good luck for the exam i'm sure you will have a big score... thanks a lot
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| meg
Forum Guru
Topics: 62
Posts: 806
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thanks mistral92 
Wish you all the best too.
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