Schilling, K. and Gratzl, Manfred
Quantification of p38/synaptophysin in highly purified adrenal medullary chromaffin vesicles.
In: FEBS Letters, Vol. 233: pp. 22-24
p38/synaptophysin is a membrane protein present
in clear (synaptic) vesicles of neurons and endocrine
ceHs [1-4]. From the amino acid sequence
deduced from cDNAs encoding p38/synaptophysin,
a model with several membrane spanning
polypeptide segments and a carboxy-terminal
protein domain exposed to the cytoplasmic surface
has been constructed [5-7].
The function of p38/synaptophysin is not
known. It has been suggested to form a transmembrane
channel for ions, or to interact with
cytoplasmic factors via its cytoplasmic domain .
Since synaptophysin binds Ca2
+, it may also play
a role in the release of neurotransmitters stored in
clear (synaptic) vesicles .
Recently it has been reported  that p38/synaptophysin
also occurs in hormone containing large
dense core vesicles. This would imply that
p38/synaptophysin could fulfill similar functions
as described above in chromaffin and other
secretory ceHs containing large dense core vesicles.
In dear (synaptic) vesicles p38/synaptophysin constitutes
7.51Jfo of the vesicle membrane proteins [I].
The amount of p38/synaptophysin in large dense
core vesides is not known. Here we report on the
quantification of p38/synaptophysin in highly
purified chromaffin secretory vesides