Evidence for two distinct intracellular pools of inorganic sulfate in Penicillium notatum
A strain of Penicillium notatum unable to metabolize inorganic sulfate can accumulate sulfate internally to an apparent equilibrium concentration 10/sup 5/ times greater than that remaining in the medium. The apparent K/sub eq/ is near constant at all initial external sulfate concentrations below that which would eventually exceed the internal capacity of the cells. Under equilibrium conditions of zero net flux, external /sup 35/SO/sub 4//sup 2 -/ exchanges with internal, unlabeled SO/sub 4//sup 2 -/ at a rate consistent with the kinetic constants with the sulfate transport system. Efflux experiments demonstrated that sulfate occupies two distinct intracellular pools. Pool 1 is characterized by the rapid release of /sup 35/SO/sub 4//sup 2 -/ when the suspension of preloaded cells is adjusted to 10 mM azide at pH 8.4 (t/sub 1/2/, 0.38 min). /sup 35/SO/sub 4//sup 2 -/ in pool 1 also rapidly exchanges with unlabeled medium sulfate. Pool 2 is characterized by the slow release of /sup 35/SO/sub 4//sup 2 -/ induced by azide at pH 8.4 or unlabeled sulfate (t/sub 1/2/, 32 to 49 min). Early in the /sup 35/SO/sub 4//sup 2 -/ accumulation process, up to 78% of the total transported substrate is found in pool 1. At equilibrium, pool 1 accounts for only about 2% of the total accumulated /sup 35/SO/sub 4//sup 2 -/. Monensin (33 ..mu..m) accelerates the transfer of /sup 35/SO/sub 4//sup 2 -/ from pool 1 to pool 2. Valinomycin (0.2 ..mu..M) and tetraphynylboron/sup -/ (1 mM) retard the transfer of /sup 35/SO/sub 4//sup 2 -/ from pool 1 to pool 2. Pool 2 may reside in a vacuole or other intracellular organelle. A model for the transfer of sulfate from pool 1 to pool 2 is presented.
- Research Organization:
- Univ. of California, Davis
- OSTI ID:
- 5094022
- Journal Information:
- J. Bacteriol.; (United States), Vol. 162:3
- Country of Publication:
- United States
- Language:
- English
Similar Records
Cl sup minus -HCO sup minus sub 3 antiport in rat lacrimal gland
METHODS IN IMMUNOCHEMISTRY OF VIRUSES. 3. SIMPLE TECHNIQUES FOR LABELING ANTI-BODIES WITH I$sup 131$ AND S$sup 3$$sup 5$
Related Subjects
59 BASIC BIOLOGICAL SCIENCES
PENICILLIUM
BIOCHEMICAL REACTION KINETICS
SODIUM SULFATES
MEMBRANE TRANSPORT
SULFUR 35
AZIDES
BIOCHEMISTRY
VALINOMYCIN
ALKALI METAL COMPOUNDS
ANTI-INFECTIVE AGENTS
ANTIBIOTICS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CHEMISTRY
DAYS LIVING RADIOISOTOPES
DRUGS
EVEN-ODD NUCLEI
FUNGI
ISOTOPES
KINETICS
LIGHT NUCLEI
NITROGEN COMPOUNDS
NUCLEI
OXYGEN COMPOUNDS
PLANTS
RADIOISOTOPES
REACTION KINETICS
SODIUM COMPOUNDS
SULFATES
SULFUR COMPOUNDS
SULFUR ISOTOPES
550601* - Medicine- Unsealed Radionuclides in Diagnostics
550201 - Biochemistry- Tracer Techniques