Evidence for Conformational Changes in Euglena Chloroplasts

Spinach chloroplasts carry out several energydependent processes such as conformational changes andl ion translocation, in a(llition to the synthesis of ATP. The evidence for energy-dependent conformational changes has come from light-scattering studies by Packer (11, 12), Jagendorf and Hind (5), and Dilley an(d Vernon (1). Itoh et al. (3) and Izawa et al. (4) have observed changes in chloroplast volume by Coulter counter studies, "chlorocrit" (leterminations, and in ultrastructure in vivo (6) and in vitro (3) by electron microscopy of illuminated spinach chloroplasts. Mukohata and Packer (8) and Ohnishi (10) have also reporte(l light-dependent viscosity changes in suspensions of spinach chloroplasts. Packer and Marchant (13) and Ohnishi (10) have extracted contractile proteins from spinach chloroplasts. Conditions similar to those required for structural changes (13) also support a light-dependent uptake of calcium and phosphate in isolated spinach chloroplasts (9). Hence, it is concluded that chloroplasts in a higher plant such as spinach should be capable of regulating both their ioln and water contents. It seemed worthwhile, therefore, to consider the possibility of the occurrence of a similar phenonmenon in algae. It has been found that Euiglenia chloroplasts show light-dependent packed volume changes an(c energy-dependent conformational changes as reveale(d by light-scattering studies.