Electrophoretic characterization of membrane proteins during chloroplast development in barley.

Abstract

Membranes of plastids isolated from greening 15-cm (6 days) barley seedling were analysed electrophoretically using acid-soaked polyacrylamide gels. During greening five new major classes of membrane-bound proteins appeared having apparent molecular weights of 100 000, 63 000, 41 000, 39 000, and 34 000, respectively. As greening progressed these proteins became the prominent feature of the electrophoretic pattern. Chloramphenicol and cycloheximide each had different inhibitory effects on the appearance of the new protein bands. Mutants of barley (xantha-f, g, h) blocked at an early stage in chloroplast development lacked the light-induced bands. Conversely, mutants xantha-b-12 and b-18 with lamellar systems organized into giant grana lacked some, but not all, of the light-induced bands. At the early stages of greening the newly formed membrane proteins and chlorophyll were inserted into existing membranes. At later stages, all membrane components appeared to be synthesized. Evidence is discussed that certain membrane proteins are specific for grana, while others are associated with stroma lamellae.