A 15 kDa proteolipid found in mediatophore preparations from Torpedo electric organ presents high sequence homology with the bovine chromaffin granule protonophore

Abstract

Upon SDS PAGE of isolated mediatophore, an acetylcholine-translocating protein, a doublet at 15 kDa was identified. Amino acid sequencing after CNBr cleavage gave a 17 residue-long peptide completely homologous with a sequence of the proton-translocating proteolipid from bovine chromaffin granules. A Sl-mer oligodeoxynucleotide corresponding to this sequence was used to screen a library of electric lobe cDNAs constructed in llZap II. A positive recombinant clone was isolated and found to encode the complete sequence of a 15.5 kDa protein highly homologous to the bovine chromaffin or yeast vacuolar ATPase proteolipid. In vitro translation of sense RNA transcripts of the clone indeed yielded a single 15 kDa proteolipid. Northern blot analysis showed that the 1.3 kb mRNA encoding this protein is significantly expressed in nervous tissues but not in electric organ or liver of Torpedo marmorata.

Specific sorting of the a1 isoform of the V-H+ATPase a subunit to nerve terminals where it associates with both synaptic vesicles and the presynaptic plasma membrane

“…Poly(A) + RNAs extracted from T. marmorata electric lobes and a T. marmorata electric lobe cDNA library constructed in λZAPII were kindly provided to us by F. M. Meunier (Birman et al, 1990). cDNAs were generated by oligo-dT-primed reverse transcription of electric lobe poly(A) + RNAs (Mo-MLV-RNAse H -reverse transcriptase from Promega).…”

The vacuolar H+-ATPase: a universal proton pump of eukaryotes

“…The 16-17 kDa subunit c of the V o sector has been widely studied, and the genes from diverse fungal [102,103], plant [104][105][106][107][108][109], arthropod [7,[110][111][112], mammalian [113][114][115] and other vertebrate [116] sources have been cloned. The 16 kDa proteolipid is one of the most conserved membrane proteins known, with greater than 65 % identity between virtually all species (M. E. Finbow and M. A. Harrison, unpublished work).…”

“…The oncogenic activity of the viral protein is dependent in part upon binding to subunit c, but the significance and nature of the binding between subunit c and synaptophysin\ synaptobrevin complexes is not understood. Subunit c is a component of the mediatophore, which has been suggested to be a site of neurotransmitter release [116] (see [123] for references). Indeed, reconstituted subunit c in liposomes is able to form an oligomeric complex that is permeable to acetylcholine and glutamate [116,137].…”

“…Subunit c is a component of the mediatophore, which has been suggested to be a site of neurotransmitter release [116] (see [123] for references). Indeed, reconstituted subunit c in liposomes is able to form an oligomeric complex that is permeable to acetylcholine and glutamate [116,137]. The question of mediatophore and neurotransmitter release has proved as controversial as ductin and gap junctions, although a recent study has shown that quantal release of acetylcholine can be achieved when subunit c is present in the cell membrane [138].…”

CpG island in the region of an autosomal dominant polycystic kidney disease locus defines the 5' end of a gene encoding a putative proton channel.

“…A similar, if not identical, H'-ATPase has been implicated in H' secretion and urinary acidification in the intercalated cells of the distal nephron (8,9). Moreover, a 16-kDa proteolipid having a highly homologous amino acid sequence has also been isolated from gap junction preparations of bovine brain (10), from yeast (11), from mediatophore preparations of Torpedo electric organ (12), and from Drosophila (13).…”