BIOL 2020 Lecture Notes - Lecture 7: Nuclear Localization Sequence, Nuclear Lamina, Nuclear Membrane
Nucleus Structure and Function
October 26-30, 2015
Nucleus: membrane bounds structure within the cell of eukaryotes
• DNA Storage
• DNA Replication
• DNA Transcription
Nuclear Structure:
• Nuclear envelope or membrane
o 2 membranes create a nuclear envelope
▪ creates a bilayer
▪ Outer = outer nuclear membrane
• Continuous with rough ER (attached) that has ribosomes attached
• Proteins are attached to actin (Nesprin 1 or 2) and intermediate filaments
(Nesprin 3)
▪ Inner = inner nuclear membrane
• Integral proteins are attached to lamina (intermediate filament networks)
made of lamins (proteins)
•
•
▪ **Fused together at ends
▪ About 60 integral membranes within nuclear envelope
▪ Proteins on inner and outer are completely different in separate functional
compartments
• Establishes intermembrane space
▪ A nuclear pore complex moves through intermembrane space (channel?)
▪ Heterochromatin
o Dynamic – assembly, disassembly, transport
▪ Mitosis or meiosis
▪ How membrane degrades and reforms
▪ Material is transported with regulative movement through the membrane
o Creates a barrier for restricted movement
• Nuclear Pore Complex (NPC)
o Can see structures in thin section electron microscope
▪ Cytoplasmic face
▪ Nuclear face
• NEL – nuclear lamina
▪ 8-fold symmetry*
o Made of proteins called nucleoporins
▪ Well conserved
▪ Phenylalanine (F) – glycine (G) repeats
• Amino acids repeats to give regions of protein enriched in phenylalanine
and glycine
• FG domains of nucleoporins attach
▪ Central scaffold (8) per unit
▪ Transmembrane ring
▪ Nuclear ring attaches to create nuclear basket
▪ Cytoplasmic filaments are attached to cytoplasmic ring
▪ Creates central channel going through both membranes
o Nuclear Localization Signals
-Lysine (K), Arginine (R) and Proline (P)
-signal sequence involved hydrophilic, positively charged lysine and arginine
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Document Summary
Nucleus: membrane bounds structure within the cell of eukaryotes: dna storage, dna replication, dna transcription. Integral proteins are attached to lamina (intermediate filament networks) made of lamins (proteins) Signal sequence involved hydrophilic, positively charged lysine and arginine protein with a nuclear localization signal the cytoplasm filaments of nuclear pore complex nuclear pore into cytoplasm. It will bind and form a complex allowing the protein to move around until it reaches. The complex gets moves into pore by interacting with fg domain of fg proteins. Released into the nucleoplasm once ran-gtp which causes dissociation of the. The ran-gtp still remains attached to the importin beta and moves back through. Short peptides (only 4-8 amino acids) * do not have to be adjacent; may be disperse. Can occur anywhere in the protein moving into nucleus. Receptors are present on the membrane to recognize proteins or signal sequence: mobile transport receptors: Importins: cytoplasm to nucleus *binds to protein in cytoplasm.
