Nuclear envelope

Two membranes with a space between them, pierced by the only route in or out, and braced against the cytoskeleton so the nucleus can be pushed around without tearing.

Where it came from

in evolution the nuclear envelope arose from the prokaryotic plasma membrane

general · review · Blobel G 2010, Cold Spring Harb Symp Quant Biol · source

Nuclear pore complexes

the only route for bidirectional macromolecular transport between cytoplasm and nucleus, and more than 500 nucleoporins make up a single pore

general · review, with crystallographic analysis of nucleoporin contact sites · Blobel G 2010, Cold Spring Harb Symp Quant Biol · source

Nuclear envelope junctions

patches of integral membrane proteins of the outer and inner membranes that interact through conserved domains in the perinuclear space, holding the two membranes closely aligned

general · review · Blobel G 2010, Cold Spring Harb Symp Quant Biol · source

What the junctions are for

they attach to repetitive heterochromatin on the nuclear side and to cytoskeletal elements on the cytoplasmic side, so force from the cytoskeleton is buffered and the nucleus can move through viscous cytoplasm without the envelope being disrupted

general · review · Blobel G 2010, Cold Spring Harb Symp Quant Biol · source

The pore is not rigid

crystallographic analysis of some nucleoporin contact sites suggests considerable plasticity, which buffers mechanical force and lets pore conformation change to carry large cargo

general · review of crystallographic work · Blobel G 2010, Cold Spring Harb Symp Quant Biol · source

Not shown yet

Eightfold symmetry of the pore ring

the copy draws eight subunits around each pore because that is the conventional depiction. No source read for this page states it, so it is drawn and not claimed.

Pore diameter, membrane spacing, pores per nucleus

none of the three is given with a method in any abstract read for this page. The copy's proportions are drawn to be legible, not to scale.

Behind the copy

The nuclear envelope is two membranes with a perinuclear space between them, and in evolution it arose from the prokaryotic plasma membrane. Three structures are associated with it. Nuclear pore complexes pierce both membranes and are the only route for bidirectional macromolecular transport between cytoplasm and nucleus; more than 500 nucleoporins make up a single pore. The nuclear lamina lies under the inner membrane. And nuclear envelope junctions are patches of integral membrane proteins of the outer and inner membranes that interact through conserved domains in the perinuclear space, holding the two membranes closely aligned; on the nuclear side they attach to repetitive heterochromatin and on the cytoplasmic side to cytoskeletal elements, so mechanical force from the cytoskeleton is buffered and the nucleus can move through viscous cytoplasm without the envelope tearing.

source 1

Other organelles

All · Autophagosome · Centrosome · Cilia and flagella · Cytoskeleton · Endosomes and vesicles · Golgi · Lipid droplet · Lysosome · Mitochondrion · Nucleolus · Nucleus · Peroxisome · Plasma membrane · Proteasome · Ribosome · Rough ER · Smooth endoplasmic reticulum

Building the copy.