In response to request for info on export of cytoplasmic proteins, yes there is
such a thing. Karl Kuchler, when he was in Jeremy Thorner's lab at Berkeley,
sequeced the STE6 gene, which turned out to be a MDR homolog. In case you
don't know, and there is no reason why you should, MDR is the multidrug
resistance gene that, when massivley amplified, results in tumor cells that are
capable of transporting cancer drugs out of the cytoplasm and are therefore
resistant to the drugs. Back to the point. STE6 is involved in transporting
the a-factor mating peptide out of the cytoplasm of yeast cells. Rachel Sterne
when she was in the Thorner lab showed quite nicely that a-factor was
cytoplasmic initially and can be exported *independently* of the SEC genes.
SEC genes encode elements of the yeast secretory pathway and are it turns out
often highly functionally and structurally similar to genes encoding proteins
involved in mamalian secretion. For more info, do a search on Kuchler and
Thorner or on Randy Shekman.
