COBRA protein

The application of this technique will also probe the localization of other proteins which are hypothesized to be components of rosette TCs in plant cells (Doblin et al. 2002 Joshi et al. 2004), the membrane-anchored glucanase (Lane et al. 2001 Molhoj et al. 2001 Sato et al. 2001 Szyjanowicz et al. 2004 Rober et al. 2005), sucrose synthase (Amoret al. 1995 Salnikov et al. 2001), and callose synthase (Cui et al. 2001 Zonglie et al. 2001a, b). A number of these proteins are important for cellulose synthesis. Recently, an Arabidopsis mutant defective in the COBRA protein was isolated (Roudier et al. 2005). This mutant exhibits disorganization of the orientation of cellulose microfibrils and subsequent reduction of crystalline cellulose. It is suggested that the COBRA protein is a GPI-anchored protein localized on the plasma membrane. This means that... 

COBRA protein is involved in the regulation of eellulose microfibril arrays and in the future it may be possible to determine the localization of this protein by SDS-FRL. 

Beta-bungarotoxin, a protein in cobra snake venom, also binds to cholinergic nerves to stop ACh release while a-bungarotoxin (from the same source) binds firmly to peripheral postsynaptic nicotinic receptors. The combined effect ensures the paralysis of the snake s victim. 

It is interesting to note that the first demonstration of tyrosinate fluorescence in a protein was made by Szabo et al.au> with two cytotoxins from the Indian cobra Naja naja. While exhibiting different relative amounts of the two emission bands, both toxins had fluorescence at 304 and 345 nm, with the 304-nm band being greatly reduced on excitation at 290 nm. Since these proteins have three tyrosine residues and no tryptophan, it was concluded that the 345-nm emission band was due to tyrosinate. Furthermore, tyrosinate appeared to be formed in the excited state from a hydrogen-bonded ground-state complex based on the absorption spectra. Szabo subsequently reexamined these peptide samples and found that they were contaminated with tryptophan (A. G. Szabo, personal communication). While Szabo s approach to the demonstration of tyrosinate fluorescence was correct based on his initial data, his subsequent finding exemplifies an important caution if tyrosinate emission is suspected, every effort must be made to demonstrate the... 

Since the rate constants of bimolecular diffusion-limited reactions in isotropic solution are proportional to T/ these data testify to the fact that the kt values are linearly dependent on the diffusion coefficient D in water, irrespective of whether the fluorophores are present on the surface of the macromolecule (human serum albumin, cobra neurotoxins, proteins A and B of the neurotoxic complex of venom) or are localized within the protein matrix (ribonuclease C2, azurin, L-asparaginase).1 36 1 The linear dependence of the functions l/Q and l/xF on x/t] indicates that the mobility of protein structures is correlated with the motions of solvent molecules, and this correlation results in similar mechanisms of quenching for both surface and interior sites of the macromolecule. 

De, P., Dasgupta, S.C., Gomes, A. (2002). A lethal neurotoxic protein from Indian king cobra (Ophiophagus hannah) venom. Indian J. Exp. Biol., 40(12), 1359-1364. 

Cobra toxin (cobrotoxin), a 62 amino acid protein with four disulfide bridges, causes nondepolarizing blockade at neuromuscular... 

Various types of proteins have been purified using hydrophobic interaction chromatography including alkaline phophatase, estrogen receptors, isolectins, strepavidin, calmodulin, epoxide hydrolase, proteoglycans, hemoglobins, and snake venom toxins (46). In the case of cobra venom toxins, the order of elution of the six cardiotoxins supports the hypothesis that the mechanism of action is related to hydrophobic interactions with the phospholipids in the membrane. 

In general, a-helix exhibits lower amide I and higher amide III frequencies than /1-sheet and random coil. However, distinction of the latter two is not clear-cut. Amide III is more structure-sensitive than amide I. For example, cobramine B, a small basic protein from cobra venom, contains a-helix, /1-sheet and random coil structures. As a result, three amide III bands are observed at 1,270 (a-helix), 1,254 (hydrogen-bonded random coil) and... 

MTLP-1 (= Muscarinic toxin-like protein)] (polypeptide) J raja kaouthia (cobra snake) mACh-R ligand - M3 (Methylscopolamine displacement) (3) [amino acid sequence homology to MTLP-2 from cobra mamba toxins MT1 MT4]... 

Eldefrawi and Eldefrawi [98] reported the purification of the acetylcholine of Torpedo electroplax on an affinity column consisting of cobra (Naja naja siamensis) toxin coupled to Sepharose 4B. Desorption with 10 mM benzoquinonium produced a protein that bound [ I]a-bungarotoxin but not [ H]acetyl-choline. However, desorption with 1 mM carbamylcholine gave a receptor protein that bound pH]acetylcholine decamethonium, [ H]nicotine [ C]dimethyl-(-l-)-tubocuranrine, and [ I]a bungarotoxin. Schmidt and Raftery [99] also purified acetylcholine receptor, from Narcine, on a N-(e-aminohexanoyl)-3-aminopropyltrimethyl-ammonium bromide-HBr-agarose column. 

Trifluoroethanol has been used to denature proteins and to stabilize structures in peptides via protonation. Direct interactions of the trifluoroethanol with the peptide chain have been inferred from changes in NMR chemical shift and line width. Site-specific interaction has not yet been demonstrated experimentally in solution [39, 40]. Neutron diffraction studies on a similar protonation of lysozyme by ethanol indicate that trifluoroethanol is likely to bind to the carbonyl oxygen on the main chain of the peptide. It is inferred that such a site-specific interacting nature of trifluoroethanol resulted in the enhancement of intramolecular hydrogen bonding of the amide group in the peptide to minimize its exposure to the alcohol. A structural transition from (3 -sheet to a -helix of the Taiwan cobra poison peptide, which is induced by an interaction of trifluoroethanol, has been reported [41 ]. Details on the effects of trifluoroethanol on peptides and proteins are summarized in Ref. [42]. 

For many who study the chemistry of venoms, the neurotoxins hold particular interest. One example would be the polypeptide toxin cobrotoxin that was isolated from the Formosan cobra and analyzed in 1965 by Chen-Chung Yang, a distingmshed chair professor at Tsing Hua University in Taiwan. The primary structure of this neurotoxin is indicated in Figure 1, along with some components of its secondary structure. There are sixty-two residues in the primary structure and four di-sulfide bonds in the secondary structure. If even one of these di-sulfide bonds is somehow disrupted, the polypeptide is rendered nontoxic. This points to the fact that secondary structure is important even in small polypeptides, not only full-size proteins. 

Ricketts, E.M. Rradshaw, J. Hann, M. Hayes, F. Tanna, N. Ricketts. D.M. Comparison of conformations of small-molecule structures from the Protein Data-Bank with those generated by concord, cobra, chemdbs-3D, and converter and those extracted from the Cambridge Structural Database. J. Chem. Inf. Comput. Sci. 1993, 33. 905-925. 

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