Ion-translocating properties of calcifiable proteolipids

Journal Article · Tue Mar 01 04:00:00 EST 1988 · J. Dent. Res.; (United States)

DOI:https://doi.org/10.1177/00220345880670030101· OSTI ID:6558953

Swain, L D; Boyan, B D

De novo formation of calcium hydroxyapatite in biological systems occurs on membrane surfaces through specific interactions of Ca, Pi, phospholipids, calcifiable proteolipids, and ion flux to and from the nucleating site. This paper reports an in vitro model demonstrating an ion transport function for calcifiable proteolipid. Bacterionema matruchotii proteolipid was incubated with a radiolabeled H+-channel inhibitor, 14C-dicyclohexyl-carbodiimide, and binding characterized by displacement studies with DCCD or ethyldimethylaminopropylcarbodiimide. A carboxyl binding site was suggested by displacement of DCCD by the nucleophile, glycine ethyl ester. The displacement studies indicated that proteolipid bound DCCD via carboxyl group interaction in a hydrophobic region of the protein. SDS-polyacrylamide gel electrophoresis showed that all label was associated with a single band of 8500 Mr. No non-specific binding of 14C-DCCD to phospholipids occurred, since all bound label was associated with protein following Sephadex LH-20 chromatography of crude proteolipid. Phospholipid liposomes were prepared containing bacteriorhodopsin and proteolipid or proteolipid-14C-DCCD, via cholate dialysis. Transmembrane pH changes established by the bacteriorhodopsin H+ pump were measured in the presence and absence of added proteolipid. Proteolipid had an effect similar to those of uncouplers such as tetraphenylboron. Both the rate and extent of proton translocation increased following addition of proteolipid to BR-liposomes. 14C-DCCD abolished the proteolipid-augmented ion transport. When tetraphenylboron was used to abolish the transmembrane electrical potential, calcifiable proteolipid did not augment proton transport.

• Research Organization: Univ. of Texas, San Antonio (USA)
• OSTI ID: 6558953
• Journal Information: J. Dent. Res.; (United States), Journal Name: J. Dent. Res.; (United States) Vol. 67:3; ISSN JDREA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
BARYONS
BIOCHEMICAL REACTION KINETICS
CARBON 14 COMPOUNDS
CELL CONSTITUENTS
CELL MEMBRANES
CHEMICAL PROPERTIES
ELECTROPHORESIS
ELECTROPHYSIOLOGY
ELEMENTARY PARTICLES
FERMIONS
HADRONS
IMIDES
IN VITRO
ISOTOPE APPLICATIONS
KINETICS
LABELLED COMPOUNDS
LIPIDS
LIPOPROTEINS
LIPOSOMES
MEMBRANE PROTEINS
MEMBRANE TRANSPORT
MEMBRANES
NUCLEONS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANOIDS
PHYSIOLOGY
PROTEINS
PROTONS
REACTION KINETICS
RECEPTORS
TRACER TECHNIQUES