2 research outputs found
Chemical Cross-Linking and H/D Exchange for Fast Refinement of Protein Crystal Structure
A combination of chemical cross-linking and hydrogen–deuterium
exchange coupled to high resolution mass spectrometry was used to
describe structural differences of NKR-P1A receptor. The loop region
extended from the compact core in the crystal structure was found
to be closely attached to the protein core in solution. Our approach
has potential to refine protein structures in solution within a few
days and has very low sample consumption
Cytotoxic Lipopeptide Muscotoxin A, Isolated from Soil Cyanobacterium <i>Desmonostoc muscorum</i>, Permeabilizes Phospholipid Membranes by Reducing Their Fluidity
There is mounting evidence that cyanobacterial
lipopeptides can
kill mammalian cells, presenting a hazard to human health. Unfortunately,
their mechanism of toxicity is poorly understood. We have isolated
new cyclic undeca-lipopeptides muscotoxin A and B containing unique
lipophilic residue 3-amino-2,5-dihydroxydecanoic acid (5-OH Ahdoa).
Muscotoxin B was not used for biological studies due to its poor yield.
Muscotoxin A was cytotoxic to YAC-1, Sp/2, and HeLa cancer cell lines
(LC<sub>50</sub> ranged from 9.9 to 13.2 μM after 24 h of exposure),
causing membrane damage and influx of calcium ions. Subsequently,
we studied this lytic mechanism using synthetic liposomes with encapsulated
fluorescent probes. Muscotoxin A permeabilized liposomes composed
exclusively of phospholipids, demonstrating that no proteins or carbohydrates
present in biomembranes are essential for its activity. Paradoxically,
the permeabilization activity of muscotoxin A was mediated by a significant
reduction in membrane surface fluidity (stiffening), the opposite
of that caused by synthetic detergents and cytolytic lipopeptide puwainaphycin
F. At 25 °C, muscotoxin A disrupted liposomes with and without
cholesterol/sphingomyelin; however, at 37 °C, it was selective
against liposomes with cholesterol/sphingomyelin. It appears that
both membrane fluidity and organization can affect the lytic activity
of muscotoxin A. Our findings strengthen the evidence that cyanobacterial
lipopeptides specifically disrupt mammalian cell membranes and bring
new insights into the mechanism of this effect