BIOB11H3 Chapter Notes - Chapter 12: Centromere, Disaccharide, Histone H2B
Document Summary
The nucleus contains chromosomes (condensed into chromatin = chromosomes + proteins), nucleoli, nucleoplasm, and nuclear matrix. The inner surface is bound by integral membrane proteins that are connected to filamentous meshwork called nuclear lamina (made up of lamins). A nuclear pore complex (npc) has an octagonal symmetry - contains only about 30 different proteins, called nucleoporins (at least 8 copies). Low-molecular-weight solutes may penetrate the nuclear pores by simple diffusion, whereas proteins and rnas have to pass throught he central channel with the help of special transport systems. The nuclear localization signal (nls) is a strech of positively charged amino acids in the c-terminus that enables proteins to pass through the nuclear pores. Mobile transport receptors include importins (move macromolecules from cytoplasm into nucleus) and exportins (opposite direction). Nls-containing cargo bind to a heterodimeric, soluble nls receptor called importin a/b in the cytoplasm.