ABSTRACT
The mutual effect of three actin-binding proteins (alpha-actinin, calponin and filamin) on the binding to actin was analyzed by means of differential centrifugation and electron microscopy. In the absence of actin alpha-actinin, calponin and filamin do not interact with each other. Calponin and filamin do not interfere with each other in the binding to actin bundles. Slight interference was observed in the binding of alpha-actinin and calponin to actin bundles. Higher ability of calponin to depress alpha-actinin binding can be due to the higher stoichiometry calponin/actin in the complexes formed. The largest interference was observed in the pair filamin-alpha-actinin. These proteins interfere with each other in the binding to the bundled actin filaments; however, neither of them completely displaced another protein from its complexes with actin. The structure of actin bundles formed in the presence of any one actin-binding protein was different from that observed in the presence of binary mixtures of two actin-binding proteins. In the case of calponin or its binary mixtures with alpha-actinin or filamin the total stoichiometry actin-binding protein/actin was larger than 0.5. This means that alpha-actinin, calponin and filamin may coexist on actin filaments and more than mol of any actin-binding protein is bound per two actin monomers. This may be important for formation of different elements of cytoskeleton.
Subject(s)
Actinin/metabolism , Actins/metabolism , Calcium-Binding Proteins/metabolism , Contractile Proteins/metabolism , Microfilament Proteins/metabolism , Actinin/isolation & purification , Animals , Calcium-Binding Proteins/isolation & purification , Chickens , Contractile Proteins/isolation & purification , Ducks , Electrophoresis, Polyacrylamide Gel , Filamins , Microfilament Proteins/isolation & purification , Protein Binding , CalponinsABSTRACT
Interaction of calponin and alpha-actinin with actin was analyzed by means of cosedimentation and electron microscopy. G-actin was polymerized in the presence of calponin, alpha-actinin, or both of these actin-binding proteins (ABPs). The single and bundled actin filaments were separated, and the stoichiometry of ABPs and actin in both types of filaments was determined. Binding of calponin to the single or bundled actin filaments was not dependent on the presence of alpha-actinin and did not displace alpha-actinin from actin. In the presence of calponin, however, less alpha-actinin was bound to the bundled actin filaments, and the binding of alpha-actinin was accompanied by a partial decrease in the calponin/actin stoichiometry in the bundles of actin filaments. Calponin had no influence on the binding of alpha-actinin to the single actin filaments. The structure of actin bundles formed in the presence of the two ABPs differed from that formed in the presence of either one singly. We conclude that calponin and alpha-actinin can coexist on actin and that nearly each actin monomer can bind one of these ABPs.
Subject(s)
Actinin/metabolism , Actins/metabolism , Calcium-Binding Proteins/metabolism , Animals , Chickens , Dose-Response Relationship, Drug , Ducks , Electrophoresis, Polyacrylamide Gel , Kinetics , Microfilament Proteins/metabolism , Microscopy, Electron , Models, Biological , Protein Binding , Rabbits , CalponinsABSTRACT
The effects of hypochlorite (HOCl/OCl-) on the content of carotenoids (trans-lycopene, 5-cis-lycopene, alpha- and beta-carotene) and oxycarotenoids (lutein, zeaxanthin, trans- and cis-2',3'-anhydrolutein, alpha-and beta-cryptoxanthin) in human blood low-density lipoproteins (LDL) were compared using HPLC. Hypochlorite decreased the content of all the above-mentioned pigments in LDL. However, it was more reactive towards carotenoids rather than to their oxy derivatives. The ability of carotenoids and oxycarotenoids to scavenge HOCl/OCl- decreases in the series: trans-lycopene approximately 5-lycopene > alpha-carotene > beta-carotene > zeaxanthin > alpha-cryptoxanthin > cis-2',3'-anhydrolutein > beta-cryptoxanthin > trans-2',3'-anhydrolutein > lutein. Preincubation of LDL with hypochlorite decreased their resistance to CU(2+)-induced accumulation of dienic conjugates that are produced in the course of lipid peroxidation. The data suggest that hypochlorite-induced destruction of carotenoids in LDL decreases their resistance to oxidative modification, thus promoting the development of early stages of atherosclerosis.
