Hopkins Marine Station Student Paper

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(full paper is archived in the Miller Library)

Title: The effect of diethylpyrocarbonate on voltage-gated potassium channels
Student Author(s): Sanghvi, Uma
Faculty Advisor(s): Gilly, William
Pages: 24
Location: Final Papers Biology 175H
Date: June 1997
Abstract: Pharmacology and site-based mutagenesis probe function of ion
channels by altering specific sites and observing changes in channel
properties. Previous studies by Spires and Begenisich (1990) showed that
external diethylpyrocarbonate (DEPC), a chemical modifier of histidine,
irreversibly reduces and slows potassium current in squid giant
axons. Examination of the amino acid sequence of the SqKv1A channel
thought to correspond to the axonal delayed rectifier K+ channel reveals a
putative external DEPC target at histidine 351 (H351) near the pore.
To examine the role of this residue in the DEPC effect, various Kv1
channels were transiently expressed in HEK 293 cells and tested for DEPC
sensitivity. It was hypothesized that this histidine is necessary for the
DEPC effect.
Although it was found that K+ channels with the proposed critical
residue exhibited a reduction in peak current after DEPC application,
similar effects were seen in clones lacking the histidine near the
external mouth of the pore. These cloned channels did have other external
histidines, however. Additionally, DEPC slowed the activation kinetics of
nearly all tested clones, in some cases without a corresponding decrease
in current amplitude. It was concluded that while modification of
histidine residues in Kv1 channels affects functional properties, all
effects cannot be attributed to modification of the residue equivalent to
H351 in squid.