X‐ray diffraction studies of the structural organisation of prolamellar bodies isolated from Zea mays

Abstract

Transmission electron microscopy (TEM) indicates that maize prolamellar bodies (PLBs) are built up of tetrapodal units based on a highly convoluted but continuous lipid bilayer exhibiting diamond cubic (Fd3m) symmetry. Such lattices are often described in terms of infinite periodic minimal surfaces (IMPS) exhibiting zero net curvature and dividing the system into two identical subvolumes. If so, X-ray diffraction measurements would be expected to index on a double-diamond (Pn3m) lattice with a unit cell length half that of the TEM lattice. Our measurements index on a Fd3m lattice with a similar repeat distance to the TEM images. The PLB membrane is thus inherently asymmetric, probably as the result of the distribution of membrane protein.z 1998 Federation of European Biochemical Societies.

Membrane geometry of ?open? prolamellar bodies

“…In the latter, tetrahedrally arranged water forms "cages" surrounding guest molecules of various sorts. Charvolin and Sadoc (1996) diagram the structural unit of open prolamellar bodies as a tetrahedral arrangement of pentagonal dodecahedra surrounding a central 16hedron (a space-filling structure described by Williams 1979), but without giving evidence. The geometry of the clathrate would be transformed into that of the prolamellar body if its dimensions were to be scaled up by nearly 100-fold, its guest molecules replaced by etioplast ribosomes and other components of the stroma phase, and the cage of water molecules, linked by hydrogen bonds, replaced by confluent tetrahedrally branched membrane tubules.…”

“…Pentagonal dodecahedra cannot alone fill space, but they can be assembled so as to circumscribe voids with 14, 15, or 16 faces (Williams 1979). 4-6.…”

“…4-6. This requires small (approximately 3 ~ distortions in the angles between the faces from those in regular pentagonal dodecahedra (Williams 1979). The hexagonal pattern is readily mimicked by pentagonal dodecahedra sharing faces to make linear columns which intersect at 120 ~ angles (Fig.…”

The relationship between different spectral forms of the protochlorophyllide oxidoreductase complex and the structural organisation of prolamellar bodies isolated from Zea mays

“…Paracrystalline plant prolamellar bodies (PLB) are built up from a network of interconnecting hollow tetrapodal units indexing on a diamond (Fd3m) cubic lattice (Williams et al 1998;Selstam et al 2007). They are formed by a reorganisation of the prothylakoid membranes of plant etioplasts.…”

Importance of the hexagonal lipid phase in biological membrane organization

“…At a microscopic level, HII structure have been observed in the ER of the retinal pigment epithelium (Yorke and Dickson, 1985) and of the plasma membrane of bladder epithelium (Hicks and Ketterer, 1970). Cubic structures ( Figure 1 ) that are dependent of non-bilayer forming lipids (Siegel, 1999) are also detected in the ER of epidermal keratinocytes (Norlen, 2001a) and in prolamellar bodies in etioplasts (Williams et al, 1998; Gunning, 2001). Furthermore, highly curved membranes like tubules of ER network (Griffing, 2010), the inner mitochondrial membrane (Van Venetie and Verkleij, 1982), or thylakoid grana margins (Murphy, 1982) are thought to be favored by an enrichment in HII forming lipid.…”