Sv. Subramanian et al., CLONING AND SEQUENCING OF PARAFUSIN, A CALCIUM-DEPENDENT EXOCYTOSIS-RELATED PHOSPHOGLYCOPROTEIN, Proceedings of the National Academy of Sciences of the United Statesof America, 91(21), 1994, pp. 9832-9836
A cDNA for parafusin, an evolutionarily conserved phosphoglycoprotein
involved in exocytosis, has been cloned and sequenced from a unicellul
ar eukaryote, Paramecium tetraurelia. A Paramecium cDNA library was sc
reened with an oligonucleotide probe synthesized to an internal amino
acid sequence of isolated parafusin. The insert was 3 kb long with an
open reading frame of 1.75 kb. Data base searches of the deduced amino
acid sequence showed that Paramecium parafusin had a 50.7% sequence i
dentity to rabbit muscle phosphoglucomutase, although no detectable ph
osphoglucomutase activity has been detected in isolated parafusin. The
deduced parafusin amino acid sequence had four inserts and two deleti
ons, which might confer on the protein Specific functions in signal tr
ansduction events related to exocytosis. Furthermore, searches for pot
ential phosphorylation sites showed the presence of a protein kinase C
site (KDFSFR) specific to parafusin. Southern blot analysis with prob
es specific for parafusin and phosphoglucomutase suggested that these
proteins were products of different genes. We propose that parafusin a
nd phosphoglucomutase are members of a superfamily that conserve homol
ogies important for the tertiary structure of the molecules.