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Molecular analysis of SAR1 ‐related cDNAs from a mouse pituitary cell line
Author(s) -
Shen Katherine A.,
Hammond Connie M.,
Moore Hsiao-Ping H.
Publication year - 1993
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(93)80423-r
Subject(s) - biology , cdna library , endoplasmic reticulum , complementary dna , saccharomyces cerevisiae , golgi apparatus , vesicular transport protein , microbiology and biotechnology , gene , biochemistry , vesicle , membrane
Vesicular transport between the endoplasmic reticulum (ER) and the Golgi in the yeast Saccharomyces cerevisiae requires a Ras‐like, small GTP‐binding protein, Sarip [1–3]. Whether a functional homologue operates in export from the ER in mammalian cells is unknown, nor is it clear if transport in other branches of the secretory pathway requires member(s) of a gene family. In this study, we used a PCR approach to examine the complexity of SAR1 ‐related sequences expressed in mammalian cells that possess multiple secretory pathways. Amplification of cDNA sequences from rodent pituitary cells with primers corresponding to two conserved GTP binding domains of Sarlp yielded several clones with sequences homologous to Sarl and/or the closely related ADP‐ribosylation factor (ARF) family. Of these, only two showed closer homologies to S. cerevisiae Sar1 than members of the ARF family and are designated as mSARa and mSARb . Northern blot analysis shows that mSARa is expressed in most tissues including liver, heart, brain, skeletal muscle and kidney. In contrast, mSARb is preferentially expressed in skeletal muscle and liver. The full‐length cDNA of mSARa isolated from a mouse pituitary AtT‐20 cDNA library encodes a protein of 198 amino acids, and is 61.6% identical to Sarlp from S. cerevisiae . Thus in contrast to the large rab family of GTP‐binding proteins, vesicular transport in mammalian cells appears to be mediated by a relatively small number of Sar1‐related proteins.