Isolation and characterization of three cDNAs coding for Rab proteins from the albumen gland of the mollusc Lymnaea stagnalis.
Three cDNA clones encoding small GTP-binding proteins, LS-Rab1, LS-Rab2 and LS-Rab18a were isolated from a cDNA library from the albumen gland of the pulmonate snail Lymnaea stagnalis. Comparison of the deduced amino acid sequences with available sequences from the EMBL/Data Bank revealed that LS-Rab1 and LS-Rab2 show a sequence identity of 89-90% to the mammalian Rab1 and Rab2 proteins, and can therefore be regarded as the L. stagnalis homologs. LS-Rab18a may be considered a new member of the Rab subfamily, closely related to mouse Rab18 (74% amino acid identity). Interestingly, LS-Rab1 and LS-Rab2 share a very high sequence conservation with their mammalian homologs (95-97%) over the first 178-191 N-terminal amino acids, whereas the C-terminal part is almost completely divergent, except for their extreme ends (2-4 amino acids). The implications of these observations for the understanding of Rab-targeting signals are discussed. The LS-rab cDNAs were expressed in COS-7M6 cells. The resulting 22-kDa products were shown to bind GTP. In the albumen gland mRNA, levels of LS-rab1 appeared to be much higher than those of LS-rab2 and LS-rab18a, suggesting an important role for the LS-Rab1 protein in the albumen gland.
Agterberg
M
M
Department of Medical Chemistry, Vrije Universiteit, Amsterdam, The Netherlands.
van Die
I
I
Yang
H
H
Andriessen
J A
JA
van Tetering
A
A
van den Eijnden
D H
DH
Ploegh
H L
HL
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002460:Cell Line; D002522:Chlorocebus aethiops; D018076:DNA, Complementary / Q000737:chemistry / Q000302:isolation & purification*; D005088:Exocrine Glands / Q000737:chemistry; D005260:Female; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression; D006160:Guanosine Triphosphate / Q000378:metabolism; D007668:Kidney; D008195:Lymnaea / Q000235:genetics*; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000378:metabolism; D017385:Sequence Homology; D014162:Transfection; D020691:rab GTP-Binding Proteins
D018076:DNA, Complementary; D012333:RNA, Messenger; C083930:rab1 protein, Lymnaea stagnalis; C083933:rab18a protein, Lymnaea stagnalis; C083931:rab2 protein, Lymnaea stagnalis; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins; D020691:rab GTP-Binding Proteins