Pigment-protein complexes of illuminated etiolated leaves.

Photoconversion of protochlorophyllide in etiolated leaves of Avena sativa L., var. Pennal or Peniarth and Phaseolus vulgare L., var. ;The Prince' results in the sequential appearance of spectrally distinct chlorophyllide complexes (Chlide 678, 684, and 672). This paper reports on the generation of similar forms in vitro, under controlled conditions, using well characterized etioplast membranes enriched in the enzyme protochlorophyllide reductase. Excess NADP(+) and NADPH stabilize complexes related to Chlide 678 and Chlide 684, respectively, whereas addition of exogenous Pchlide induces formation of a species related to Chlide 672. Evidence is provided to support the suggestion that Chlide 678 and Chlide 684 represent ternary complexes of the enzyme protochlorophyllide reductase, with Chlide and either NADP(+) (Chlide 678) or NADPH (Chlide 684). Chlide 672 is seen as ;free' pigment dissociated from the enzyme. The role of Pchlide in this dissociation, observed spectroscopically as the ;Shibata shift,' is discussed.