||Budding yeast Saccharomyces cerevisiae
||West M, Zurek N, Hoenger A, Voeltz GK. A 3D analysis of yeast ER structure reveals how ER domains are organized by membrane curvature. J Cell Biol. 2011 Apr 18 193(2):333-46. doi: 10.1083/jcb.201011039 p.343 right column bottom paragraphPubMed ID21502358
||Abstract: "[Investigators] analyzed the structure of yeast endoplasmic reticulum (ER) during six sequential stages of budding by electron tomography to reveal a three-dimensional portrait of ER organization during inheritance at a nanometer resolution. [They] have determined the distribution, dimensions, and ribosome densities of structurally distinct but continuous ER domains during multiple stages of budding with and without the tubule-shaping proteins, reticulons (Rtns) and Yop1."
||P.343 right column bottom paragraph: "The pmaER has many surprising features. It is made up of both tubules and fenestrated cisternae, which are so tightly linked to the PM [plasma membrane] that ribosomes are excluded between the two membranes (Fig. 1, E–G). The pmaER covers ∼20–40% of the PM in wt cells (varies with bud size, Fig. 4 H). Direct contacts between the PM and pmaER membranes can occasionally be found when [investigators] search for them (Fig. S5 A). Together, these data reveal a large pmaER–PM domain that may be unavailable for processes like vesicle-directed endocytosis and secretion. Indeed, within [their] tomograms, [they] have only observed invaginations of the PM at regions of the PM that are not bound by the ER (for an example see Fig. S5 B). The proteins that maintain this pmaER–PM domain have not been identified."