THE NUCLEAR ENVELOPE,

NUCLEAR LAMINA & PORE COMPLEX

TOPICS TO COVER:Nuclear envelope:

Nuclear membranes – inner & outer membranes.

Nuclear lamina Nuclear pore complexes

– structure – function

NUCLEAR ENVELOPE

Nuclear envelope : consists of two nuclear membranes that envelops the nucleus of an eukaryotic cell, an underlying nuclear lamina, and nuclear pore complexes.

Encloses nuclear DNA. Defines the nuclear compartment. Separates nucleus and cytoplasmic contents separate

metabolic compartments. Structural framework for nucleus.

TOPICS TO COVER:Nuclear envelope:

Nuclear membranes – inner & outer membranes.

Nuclear lamina Nuclear pore complexes

– structure – function

NUCLEAR MEMBRANES:2 lipid bilayer membranes: •Punctured nuclear pores connect the two membranes. •Different in protein composition•Separated by perinuclear space

Inner membrane – associated with nuclear lamina Outer membrane – continuous with endoplasmic reticulum

NUCLEAR MEMBRANES:

TOPICS TO COVER:Nuclear envelope:

Nuclear membranes – inner & outer membranes.

Nuclear lamina Nuclear pore complexes

– structure – function

NUCLEAR LAMINA•Intermediate filaments & membrane associated proteins(Lamins & nuclear lamin-associated membrane proteins)•Lamin types: A, B1, B2, & C•Mechanical support•Regulates cellular events

TOPICS TO COVER:Nuclear envelope:

Nuclear membranes – inner & outer membranes.

Nuclear lamina Nuclear pore complexes

– structure – function

STRUCTURE OF THE NUCLEAR PORES:

•Large compared to other proteins.•Octagonal symmetry.•Mass approx. 125 megaDaltons in vertebrates.•Cytoplasmic fibrils (tentacle-like)•Nuclear meshwork

STRUCTURE OF NUCLEAR PORE

STRUCTURE OF NUCLEAR PORE

FUNCTION OF NUCLEAR PORE

FUNCTION OF THE NUCLEAR PORE

Passive diffusion of low molecular weight solutes

Regulated transport of macromolecules larger than 40 kDa

Nuclear import signal: NLS Nuclear export sequence: NES Importins: cytoplasm to nucleoplasm Exportins: nucleoplasm to cytoplasm GTPase Ran controls interactions of cargo

and karyopherin