Structural analysis of photosystem II in far‐red‐light‐adapted thylakoid membranes

Abstract

We studied two-dimensional crystals of the major pigment±protein complex, photosystem II, in far-red-lightadapted thylakoid membranes of the viridis-zb63 mutant of barley. Significantly larger grana membranes were produced with an increased synthesis of the entire photosystem II complex. These red-light-adapted membranes also contained two-dimensional crystals with a high frequency. Three different crystal forms of photosystem II were observed, providing the following data which further our understanding of the architecture of the native complex. (a) The oligomeric form of photosystem II in the membrane was monomeric in all crystal forms, but with a clear non-crystallographic pseudo-twofold symmetry. This was more apparent on the lumenal face of the complex. (b) The variability of unit cell contacts in different crystal forms implied that the peripheral lightharvesting antenna complex and the core of the complex were loosely connected. These peripheral subunits were predicted to rearrange so that they can either encircle the core complex or associate in parallel channels separated by lines of core complexes. (c) Grana membranes were found to retain a double-layered inside-out character, with a stromal face-to-stromal face packing. However, the presence of a crystal in one membrane did not necessarily impose crystallinity on its pair.

Arrangement of photosystem II supercomplexes in crystalline macrodomains within the thylakoid membrane of green plant chloroplasts

“…Lattices with dimensions similar to those of our small-spaced crystals have been observed quite often (e.g. see Miller, 1976;Seibert et al, 1987;Vallon et al, 1989;Marr et al, 1996;Lyon, 1998;Stoylova et al, 2000). Because some of these small-spaced and large-spaced lattices were obtained without any involvement of detergent, we suggest that both types of lattices represent native states of PSII arrangement in the thylakoid membrane.…”

Organization of protein complexes and a mechanism for grana formation in photosynthetic membranes as revealed by cryo‐electron microscopy

“…Moreover, the higher resolution and better preservation of the sample in the Daum study allowed the visualisation of particles corresponding to membrane‐embedded protein complexes, with the same complexes appearing in both the thin sections as well as in the isolated membranes . Previous biochemical and structural studies , as well as X‐ray crystal structures allowed the assignment of some of the more distinctive particles within the thylakoid membranes as photosystem II complexes and CF 1 CF 0 ATP synthase complexes . A similar tomographic reconstruction of detergent‐extracted membranes was also able to resolve individual photosystem II complexes .…”