to dissect the synaptic vesicle cycle for functional 
studies. 
Dr. Jahn is also Associate Professor of Pharma- 
cology and Cell Biology at Yale University School 
of Medicine. 
Books and Chapters of Books 
Jahn, R., and De Camilli, P. 1991 . Membrane pro- 
teins of synaptic vesicles: markers for neurons and 
neuroendocrine cells, and tools for the study of 
neurosecretion. In Markers for Neural and En- 
docrine Cells: Molecular and Cell Biology, 
Diagnostic Applications (Gratzl, M., and Lang- 
ley, K., Eds.). Weinheim, FRG: VCH, pp 23-92. 
Articles 
Brose, N., Petrenko, A.G., Sudhof, T.C., and Jahn, 
R. 1992. Synaptotagmin: a calcium sensor on the 
synaptic vesicle surface. Science 256:1021- 
1025. 
Cameron, P.L., Sudhof, T.C., Jahn, R., and De Ca- 
milli, P. 1991. Colocalization of synaptophysin 
with transferrin receptors: implications for synap- 
tic vesicle biogenesis. / Cell Biol 1 15:151-164. 
Hell, J.W., Edelmann, L., Hartinger, J., and Jahn, 
R. 1991. Functional reconstitution of the 7- 
aminobutyric acid transporter from synaptic vesi- 
cles using artificial ion gradients. Biochemistry 
30:11795-11800. 
Matteoli, M., Takei, K., Cameron, R., Hurlbut, P., 
Johnston, P. A., Sudhof, T.C., Jahn, R., and De 
Camilli, P. 1991- Association of rab3A with syn- 
aptic vesicles at late stages of the secretory path- 
way. / Ce// S/o/ 115:625-633. 
Schnefel, S., Zimmermann, P., Profrock, A., Jahn, 
R., Aktories, K., Hinsch, K.D., Haase, W., and 
Schulz, I. 1992. Multiple small and high molecu- 
lar weight GTP-binding proteins in zymogen 
granule membranes of rat pancreatic acinar cells. 
Cell Physiol Biochem 2:77-89. 
Suburo, A.M., Wheatley, S.C., Horn, D.A., Gibson, 
S.J., Jahn, R., Fischer-Colbrie, R., Wood, J.N., 
Latchman, D.S., and Polak, J. 1992. Intracellular 
redistribution of neuropeptides and secretory 
proteins during differentiation of neuronal cell 
lines. Neuroscience 46:881-889. 
MOLECULAR STUDIES OF VOLTAGE-SENSITIVE POTASSIUM CHANNELS 
Lily Y. Jan, Ph.D., Investigator 
Voltage-sensitive potassium channels represent a 
diverse group of ion channels that serve a variety of 
cellular functions, ranging from secretion control in 
certain animal cells to movement control of leaflets 
and stomal pores in plants. In the nervous system, 
potassium channels control excitability and modu- 
late the strength of signaling between nerve cells; 
some potassium channels have been implicated in 
the processes of learning and memory. Since the 
cloning of Shaker, a potassium channel gene in Dro- 
sophila, a number of laboratories have cloned potas- 
sium channel genes from a variety of species ranging 
from snail to humans. The same basic design is pres- 
ent in all but one of these potassium channels, as 
well as in potassium channels in plants. Thus infor- 
mation concerning the structure-function relation- 
ship gleaned from studies of potassium channels 
such as those encoded by Shaker is likely to be of 
general interest. A summary of these structure- 
function studies is given below, followed by a pro- 
gress report on the studies of potassium channel reg- 
ulation in the mammalian brain. 
Subunit Structure of a Potassium Channel 
The polypeptides that form a potassium channel 
are much smaller than those that form a sodium or 
calcium channel and correspond to roughly one- 
quarter of the latter, suggesting that a potassium 
channel is likely to be a tetramer. Dr. Ehud Isacoflf 
further showed that heteromultimeric potassium 
channels with novel properties form in Xenopus 
oocytes, if he injected into the oocytes either two 
different mRNA species or mRNA for a tandem 
dimer. Studies from several laboratories revealed 
that only polypeptides from the same potassium 
channel subfamily can form heteromultimeric chan- 
nels; these polypeptides share ~70% amino acid 
identity in the hydrophobic core region, in contrast 
to the ~40% identity between polypeptides that be- 
long to different subfamilies. Recently Dr. Min Li 
has shown that the hydrophilic amino-terminal do- 
main of the Shaker potassium channel polypeptide 
is important in mediating the association of potas- 
sium channel subunits. Moreover, when he used the 
Shaker amino-terminal domain to replace the 
NEUROSCIENCE 409 
