Interaction of aldolase with actin-containing filaments. Structural studies.
Electron micrographs of the paracrystals formed when fructose bisphosphate aldolase (EC 4.1.2.13) is added to actin-containing filaments were analysed by computer methods so that ultrastructural changes could be correlated with the various stoicheiometries of binding determined in the preceding paper [Walsh, Winzor, Clarke, Masters & Morton (1980) Biochem. J. 186, 89-98]. Paracrystals formed with aldolase and either F-actin or F-actin-tropomyosin have a single light transverse band every 38 nm, which is due to aldolase molecules cross-linking the filaments. In contrast, the paracrystals formed between aldolase and F-actin-tropomyosin-troponin filaments show two transverse bands every 38 nm: a major band, interpreted as aldolase binding to troponin, and a minor band, interpreted as aldolase cross-linking the filaments. The intensity of the minor band varies with Ca2+ concentration, being greatest when the Ca2+ concentration is low. A model for the different paracrystal structures which relates the various patterns and binding stoicheiometries to structural changes in the actin-containing filaments is proposed.
D000199:Actins / Q000378:metabolism*; D000818:Animals; D002118:Calcium; D055598:Chemical Phenomena; D002621:Chemistry; D003201:Computers; D005634:Fructose-Bisphosphate Aldolase / Q000378:metabolism*; D008854:Microscopy, Electron; D008958:Models, Molecular; D011485:Protein Binding; D011817:Rabbits; D014335:Tropomyosin / Q000378:metabolism; D014336:Troponin / Q000378:metabolism
D000199:Actins; D014335:Tropomyosin; D014336:Troponin; D005634:Fructose-Bisphosphate Aldolase; D002118:Calcium