1. Cell Biology 17 - Organelle 1 st Sung Youn Lee, PhD. Student Veterinary collage, Room 320 02 450 3719, 016 293 6059 leevet@paran.com

2. The cell nucleus

3. Nuclear envelope Nearly all of the cellular DNA in the nucleus in eukaryotic cell. Bilayer : –Inner membrane : contact with a meshwork of intermediate filament, the nuclear lamina –Outer membrane : contiguous with the membrane of the endoplasmic reticulum (ER) –Periplasmic space : between the inner and outer membranes Components : –DNA –RNA –Nuclear proteins (structural proteins, DNA and RNA polymerase, RNA-processing proteins, histones, and gene regulatory proteins) are synthesized in the cytoplasm on free ribosomes and are brought into the nuclear compartment. Nuclear pore : continues

7. Nuclear pore Ions and small molecules (9nm diameter ( prevent bulk exchage 60kDa selective transport across the nuclear membrane, receptor mediated process Ex1, nucleoplasmin, 165-kDa, in frog oocyte nuclei –EM labeled with gold particle –COOH-terminal region (signal peptide) –ATP dependent Multistep pathway – GTP mediated

12. Structural protein of nuclear lamina & matrix 10nm filament --> square latticework Lamin A Lamin B – membrane-binding sequence, isoprenyl group which allows membrane lipid attachment Lamin C Gene, alternative splicing (A,C) and distinct gene (B) The biochemical function of the nuclear matrix is unclear. – heterogenous nuclear RNA(hnRNA) are enriched in nuclear matrix --> RNAs don’t diffuse within nucleoplasm and they are bound to nuclear matrix as they are spliced to be mature form

13. 1-condensation of chromosome 2-breakdown of nuclear envelope Lamin kinase -->Lamin A,B,C phosphorylate -->depolymerisation of nuclear lamina Lamin B remains associated with nuclear envelope Lamin A & C are dispersed within the prometaphase cell.

14. Genome Nucleus contains almost all of the genetic information of the cell in the form of DNA. The total genetic information stored within the chromosome --> genome 3 functional domains –Origin : point of initiation –Kinetochore : attachment for mitotic spindle –Telomere : maintenance of chromosomal structure, CG repeats enriched Chromatin : DNA + Protein (histone+nonhistone protein)

16. Right handed corner = sex chromosome

20. Chromosomal protein Histone protein –only in eukaryotic cell –The most abundant protein –rich (+) charge arginine & lysine, so can bind to (-) charged DNA –5 types histones ; H1, H2A, H2B, H3 and H4 -- > nucleosomal histones ; formation of nucleosome Nonhistone protein –Structural protein (HMG), regulatory protein (Fos, Myc), Enzymes (RNA & DNA polymerase)

21. Chromatin Heterochromatin –Highly condense –Transcriptionally inactive –Little heterochromatin is present in transcriptionally active cell (spermatozoa). –Lacated periphery and around nucleolus Euchromatin –More extended dispersed conformation –Transcriptionally active –Providing RNA molecules

25. Nucleolus Dense nuclear organelle Function ; Production of ribosomal subunits 4 distinct regions –Pale-staining fibrillar center / Dense fibrillar core or center(ribosomal gene transcription) / Granular region (assemble rRNAs with proteins) / Nuclear matrix The size and shape of nucleolus is dependent on its activity. –Cell, that synthesizing large amount of proteins, has the nucleolus may occupy up to 25% of the total nuclear volume.

29. Organelles involved in macromolecular synthesis and turnover

30. Ribosomes Ribosomes serve as catalysts of protein synthesis. Small subunit (40S) and Large subunit (60S) form an 80S ribosome. Membrane bound or free Proteins synthesized at membrane bound ribosomes ; integral transmembrane proteins, ER, Golgi complex, endosomal, lysosomal and secretory proteins Proteins synthesized at free ribosomes ; cytosolic proteins, peropheral membrane proteins, some nucleus proteins, mitochondria and peroxisomes.

31. Protein targeting 1.Most transmembrane proteins and membrane lipids are synthesized within the ER. 2.The targeting of membrane proteins to specific sites such as the ER, Golgi, lysosomes, or plasma membrane requires specific signal sequence within newly synthesized protein. 3.Default pathway : -ER associated ribosome ; ER --> Golgi --> secretory vesicles --> cell surface -free ribosome ; ribosome --> cytosol 4.To avoid a constantly increasing plasma membrane surface area, membrane is recycled by endocytosis.

33. Protein targeting Pulse-Chase experiment Radioactive amino acid [3H]leucine pulsechase

34. Endoplasmic reticulum RER and SER Except skeletal muscle, SER is continuous with the RER. SER is referred to as the transitional elements. (buds off, vesicle, to Golgi apparatus) 50% of the total cellular membrane Function –Protein synthesis ; RER –Lipid synthesis ; RER and SER, phospholipids steroids, triglyceride –Detoxification ; cytochrome P450 electron transfer chain

36. Signal peptides BIP ; binding protein In ER lumen, BIP binds to unfold protein and catalyst protein folding 16~30 amino acids Signal peptidase

37. Integral membrane protein Simple case(A); 20-30 hydrophobic amino acids in its NH2 terminal and it is not cleaved by signal peptidase / -COOH terminal is on the lumen Slightly more complicated case(B,C) ; two mechanism –Cleaved peptide on lumen –Similar to the mechanism of peptide into lumen

38. Into lumen – 內로 유도만함 Intergral – 內  外

39. Glycosylation N-linkedO-linked Sugar bindAsn-NH2Serine-OH Threonine-OH Where?ERGolgi apparatus How?14-sugar andOne-by-one trime

40. Long-chain unsaturated hydrocarbon

42. Glycosylphosphatidyl- inositol anchors

43. Thank you for your attention ~