Vedovato N, Baldini C, Toniolo C, Rispoli G.Alamethicin :
Pore-forming properties F50/5 inserted in a biological membrane.
Chem Biodivers. 2007 Jun;4(6):1338-46.
CNISM, Dipartimento di Biologia, Sezione di Fisiologia
e Biofisica and Centro di Neuroscienze, Università di Ferrara,
Ferrara, Italy.
The pore-forming properties of native and synthetic alamethicins
were investigated in photoreceptor rod outer segments (OS)
isolated from frog retina, and recorded in whole-cell
configuration. The peptaibols were applied (and removed) to
(from) the OS within less than 50 ms by means of a
computer-controlled micro-perfusion system. Once blocked with
light, the main OS endogenous conductance, the OS membrane
resistance was >1 GOmega, allowing low-noise and high-resolution
recordings. Currents of ca. 700 pA were recorded in symmetric
K(+) (100 mM) and Ca(2+) (1 mM), upon applying 1 microM of
alamethicin F50/5 or its [L-Glu(OMe)(7,18,19)] analogue to the
OS membrane (clamped at -20 mV). In the latter peptide, the Gln
residues at positions 7, 18, and 19 were substituted with
side-chain esterified Glu residues. For both peptides, the
current activated exponentially, with a delay from peptide
application, and exponentially returned to zero without any
delay, upon removing the peptide from the external solution. The
delay as well as the activation (tau(a)) and deactivation (tau(d))
time constants of the current produced by the modified
alamethicin were much slower, and the current noise was much
larger, with respect to the corresponding values for alamethicin
F50/5. Therefore, the above three Gln residues are not a key
factor for pore formation, but the [L-Glu(OMe)(7,18,19)]
analogue produces larger pores with a lower probability of
formation.
PMID: 17589885
|
