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Light-induced DELTApH and DELTApsi in halobacterial vesicles related to sodium transport

Technical Report ·
OSTI ID:6999731
; ;

Membranes of Halobacterium halobium contain two retinoproteins, baceteriorhodopsin (BR/sub 568nm/) and halorhodopsin (HR/sub 588nm/). We have investigated the light- and sodium-dependent activities in vesicles from the HR containing R/sub 1/mR strain, and the BR + HR containing S/sub 9/ strain to study energy conversion and ion flow mechanisms. Simultaneous ..delta..pH and ..delta..psi measurements have been made with electrodes. In R/sub 1/mR vesicles, -..delta..psi and H/sup +/ uptake occurs in NaCl but not in KCl medium. In S/sub 9/ vesicles, net H/sup +/ extrusion is reduced at high light intensity in NaCl but not KCl medium. Such results indicate Na/sup +//H/sup +/ exchange in vesicles from both strains. As S/sub 9/ contains BR + HR, it is unclear whether the Na/sup +/ extrusion is due to a Na/sup +//H/sup +/ antiporter and/or HR which has been proposed to be a light driven Na/sup +/ pump. To evaluate these concepts for Na/sup +/ transport, the light intensity dependence and action of several membrane transport active agents have been compared. Digitoxin, electro-neutral exchangers (triphenyltin and monensin), and phloretin yielded similar results for HR (R/sub 1/mR) and HR + BR (S/sub 9/) vesicles. Moreover treatment of vesicles with carboxyl reacting reagents inhibited Na/sup +/ dependent activity in both types of vesicles. Thus, common mechanisms of Na/sup +/ transport are indicated in S/sub 9/ and R/sub 1/mR vesicles. 22 refs., 9 figs., 1 tab.

Research Organization:
Lawrence Berkeley Lab., CA (USA)
DOE Contract Number:
AC03-76SF00098
OSTI ID:
6999731
Report Number(s):
DOE/SF/00098-T10; ON: DE87003013
Country of Publication:
United States
Language:
English

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Related Subjects

550500* -- Metabolism
550700 -- Microbiology
59 BASIC BIOLOGICAL SCIENCES
ALKALI METAL COMPOUNDS
BACTERIA
CELL CONSTITUENTS
CHLORIDES
CHLORINE COMPOUNDS
ELECTROPHYSIOLOGY
HALIDES
HALOGEN COMPOUNDS
LIPOSOMES
MEMBRANE PORES
MEMBRANE TRANSPORT
MICROORGANISMS
ORGANIC COMPOUNDS
ORGANOIDS
PH VALUE
PHYSIOLOGY
PIGMENTS
PROTEINS
RHODOPSIN
SODIUM CHLORIDES
SODIUM COMPOUNDS