@article {3851,
	title = {Ferintoic acids A and B, new cyclic hexapeptides from the freshwater cyanobacterium Microcystis aeruginosa},
	journal = {Journal of Natural Products},
	volume = {59},
	number = {6},
	year = {1996},
	note = {ISI Document Delivery No.: UT658Times Cited: 23Cited Reference Count: 30},
	month = {Jun},
	pages = {570-575},
	type = {Article},
	abstract = {The cyclic hexapeptides ferintoic acids A (1) and B (2) have been isolated from cells of Microcystis aeruginosa harvested during a natural bloom of the toxic cyanobacterium. The structures of 1 and 2 were determined by a combination of spectroscopic analysis and chemical degradation.},
	keywords = {AMINO-ACIDS, BLUE-GREEN-ALGA, INHIBITOR, LR, PEPTIDE, PHASE, PROTEIN PHOSPHATASES, SPONGE THEONELLA SP, TOXIN},
	isbn = {0163-3864},
	url = {<Go to ISI>://A1996UT65800004},
	author = {Williams, D. E. and Craig, M. and Holmes, C. F. B. and Andersen, R. J.}
}
@article {3640,
	title = {Molecular mechanisms underlying the interaction of motuporin and microycystins with type-1 and type-2A protein phosphatases},
	journal = {Biochemistry and Cell Biology-Biochimie Et Biologie Cellulaire},
	volume = {74},
	number = {4},
	year = {1996},
	note = {ISI Document Delivery No.: VX367Times Cited: 61Cited Reference Count: 35},
	pages = {569-578},
	type = {Article},
	abstract = {Heptapeptide microcystin and pentapeptide motuporin (nodularin-V) are equipotent inhibitors of type-1 and type-2A protein phosphatase catalytic subunits (PP-1c and PP-2Ac). Herein we describe elucidation of the molecular mechanisms involved in the interaction of these structurally similar hepatotoxins with PP-1c/PP-2Ac and identification of an important functional difference between their mode of interaction with these enzymes. Microcystin-LR, microcystin-LA and microcystin-LL were found to interact with PP-2Ac and PP-1c by a two-step mechanism involving rapid binding and inactivation of the protein phosphatase (PPase) catalytic subunit, followed by a slower covalent interaction (within hours). Covalent adducts comprising PPase-toxin complexes were separated from free PPase by C-18 reverse-phase liquid chromatography, thus allowing the time course of covalent adduct formation to be quantitated. In contrast to microcystins, motuporin (nodularin-V) and nodularin-R were unable to form covalent complexes with either PP-1c or PP-2Ac even after 96 h incubation. Specific reduction of microcystin-LA to dihydromicrocystin-LA abolished the ability of the toxin to form a covalent adduct with PP-2Ac. Specific methyl esterification of the single Glu residue in microcystin-LR rendered this toxin inactive as a PPase inhibitor and abolished subsequent formation of a covalent adduct. Our data indicate that inactivation of PP-2Ac/PP-1c by microcystins precedes covalent modification of the PPases via a Michael addition reaction between a nucleophilic phosphatase residue and Mdha in the heptapeptide toxin. In contrast, following rapid inactivation of PP-2Ac/PP-1c by motuporin, the equivalent N-methyldehydrobutyrine residue in this toxin is unreactive and does not form a covalent bond with the PPases. These results are consistent with structural data for (i) the NMR solution structures of microcystin-LR and motuporin, which indicate a striking difference in the relative positions of their corresponding dehydroamino acids in the toxin peptide backbone, and (ii) X-ray crystallographic data on an inactive complex between PP-1c and microcystin-LR, which show a covalent bond between Cys-273 and the bound toxin.},
	keywords = {BLUE-GREEN-ALGAE, CATALYTIC SUBUNIT, cyanobacteria, IDENTIFICATION, MICROCYSTIN-LR, microcystins, motuporin, nodularin, OKADAIC ACID, PHOSPHORYLATION, POTENT INHIBITOR, PROTEIN, PROTEIN PHOSPHATASES, RAT-LIVER, TOXINS},
	isbn = {0829-8211},
	url = {<Go to ISI>://A1996VX36700017},
	author = {Craig, M. and Luu, H. A. and McCready, T. L. and Williams, D. and Andersen, R. J. and Holmes, C. F. B.}
}
@article {3234,
	title = {COMPARISON OF THE SOLUTION STRUCTURES OF MICROCYSTIN-LR AND MOTUPORIN},
	journal = {Nature Structural Biology},
	volume = {2},
	number = {2},
	year = {1995},
	note = {ISI Document Delivery No.: RF665Times Cited: 1Cited Reference Count: 15},
	month = {Feb},
	pages = {114-116},
	type = {Letter},
	abstract = {A comparison of the structures of two cyanobacterial toxins yields insights into how they may inhibit protein phosphatase-1 and -2A and why microcystins but not motuporin may covalently modify their protein phosphatase targets.},
	keywords = {INHIBITOR, nodularin, POTENT, PROTEIN PHOSPHATASES, TOXINS},
	isbn = {1072-8368},
	url = {<Go to ISI>://A1995RF66500006},
	author = {Bagy, J. R. and Sonnichsen, F. D. and Williams, D. and Andersen, R. J. and Sykes, B. D. and Holmes, C. F. B.}
}
