Previous Article | Next Article ![]()
Molecular and Cellular Biology, November 2000, p. 7893-7902, Vol. 20, No. 21
Departments of Biochemistry and Molecular
Biology1 and Environmental Health
Sciences,2 Johns Hopkins University School
of Public Health, Baltimore, Maryland 21205
Received 7 June 2000/Returned for modification 13 July
2000/Accepted 31 July 2000
The baker's yeast Saccharomyces cerevisiae expresses
three homologues of the Nramp family of metal transporters: Smf1p,
Smf2p, and Smf3p, encoded by SMF1, SMF2, and
SMF3, respectively. Here we report a comparative analysis
of the yeast Smf proteins at the levels of localization, regulation,
and function of the corresponding metal transporters. Smf1p and Smf2p
function in cellular accumulation of manganese, and the two proteins
are coregulated by manganese ions and the BSD2 gene
product. Under manganese-replete conditions, Bsd2p facilitates
trafficking of Smf1p and Smf2p to the vacuole, where these transport
proteins are degraded. However, Smf1p and Smf2p localize to distinct
cellular compartments under metal starvation: Smf1p accumulates at the
cell surface, while Smf2p is restricted to intracellular vesicles. The
third Nramp homologue, Smf3p, is quite distinctive. Smf3p is not
regulated by Bsd2p or by manganese ions and is not degraded in the
vacuole. Instead, Smf3p is down-regulated by iron through a mechanism
that does not involve transcription or protein stability. Smf3p
localizes to the vacuolar membrane independently of metal treatment,
and yeast cells lacking Smf3p show symptoms of iron starvation. We
propose that Smf3p helps to mobilize vacuolar stores of iron.
0270-7306/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Saccharomyces cerevisiae Expresses Three
Functionally Distinct Homologues of the Nramp Family of Metal
Transporters
and
*
Corresponding author. Mailing address: Johns Hopkins
University School of Public Health, 615 N. Wolfe St., Room 7032, Baltimore, MD 21205. Phone: (410) 955-3029. Fax: (410) 955-0116. E-mail: vculotta{at}jhsph.edu.
Present address: Digene Corporation, Gaithersburg, Md.
This article has been cited by other articles:
| J. Bacteriol. | J. Virol. | Eukaryot. Cell |
|---|
| Microbiol. Mol. Biol. Rev. | Clin. Vaccine Immunol. | All ASM Journals |
|---|