Exam 4! Any slide that has no information for it was either self-explanatory or had no additional information in the bookLecture 29•Slide 17•Video microscopy shows flagellar movements that propel sperm and Chlamydomonas forward•Slide 18•Slide 19•Slide 20•Slide 21•Axonemal dynein attached to an A tubule of an outer doublet pulls on the B tubule of the adjacent tubule trying to move to the (-) end•Because the adjacent tubules are tethered by nexin, the force generated by dynein bends the cilium or flagellum•Slide 22•Slide 23Lecture 30•Slide 1•Slide 2•contain the ATPase activity and are thus responsible for generating movement along the microtubule•* remember: dynein is a motor protein in cells which converts ATP into the mechanical energy of movement. Dynein transports various cellular cargo by "walking" along cytoskeletal MTʼs towards the minus-end of the microtubule. Thus, they are called "minus-end directed motors," while kinesins are motor proteins that move toward the microtubules' plus end, are called plus-end directed motors.•Slide 3•The left image shows dynein in the ADP-Pi state, which represents the prestroke state, and the right image in a nucleotide free poststroke state•The force generation mechanism involves a change in orientation of the head relative to the stem, causing a movement of the MT-binding stalk•Slide 4•Organelle transport by MT motors•Slide 5•previous slide set•Slide 6•remember the basal body is an organelle formed from a centriole, and a short cylindrical array of MTʼs•It is found at the base of the cilium or flagellum and serves as the nucleation site for the growth of the axoneme MTʼs•Slide 7•structural organization of cilia and flagella•Slide 8•Electron micrograph of 2 doublet MTs in a protease-treated axoneme incubated with ATP•In the absence of cross-linking proteins, doublet MTs slide excessively •The dynein arms can be seen projecting from A tubules and interacting with B tubules on the left MT doublet•Slide 9•Activation of dynein bends MT doublets; Motor walks towards (-) end, constrained by nexin links•Nexin links are removed by protease•Activation of dynein causes MTs to slide past one another•Slide 10•Intermediate filaments (IFs) are unpolarized, have no motors•Slide 11• Slide 12•Structure and assembly of intermediate filaments•a)IF proteins form paralell dimers•b) a tetramer is formed by antiparallel, staggered aggregation side-by-side of 2 identical dimers•c) tetramers aggregate end to end and laterally into a protofibril•Slide 13•Slide 14•Keratin IFs are dynamic as soluble keratin is incorporated into filaments•Monomeric type 1 keratin was purified, chemically labeled with biotin, and microinjected into living epithelial cells•a) At 20 min, the injected biotin-labeled kertin is concentrated in a small area, it has not been integrated into the keratin cytoskeleton•b) By 4 hours, the biotin-labeled and the keratin filaments display identical patterns, indicating that the injected protein has become incorporated into the existing cytoskeleton •Slide 15•Lamins are the most widespread IFs •they provide strength and support to the inner surface of the nuclear membraneLecture 31•Slide 1•Slide 2•previous slide set•Slide 3•Slide 4•Slide 5•Slide 6•Remember:•nuclear envelope is a double lipid bilayer that encloses the genetic material in all eukaryotic cells•nucleolus is a non-membrane bound structure composed of proteins and nucleic acids found within the nucleus•rRNA is transcribed and assembled within the nucleolus •chromatin is the combination of DNA and proteins that make up the contents of the nucleus of a cell•Slide 7•dark staining areas in the Nucleus (N) outside the nucleolus (n) are heterochromatin.•The light-staining, whitish areas are euchromatin•Slide 8•Cajal bodies are spherical sub-organelles found in the nucleus of cell like embryonic cells, tumor cells, and neurons.•They lack any phospholipid membrane•Cajal bodies and speckles are just subnuclear bodies•Slide 9•During interphase, human chromosomes remain in specific territories in the nucleus•Slide 10•Slide 11•Nucleosomes are the basic unit of DNA packaging in eukaryotic cells, consisting of a segment of DNA wound around a histone protein core•nucleosomes form the fundamental repeating units of eukaryotic chromatin that is used to pack the large genomes into the nucleus•A chromosome is an organized structure of DNA and protein found in cells•histones are proteins in nuclei that package and order the DNA into nucleosomes•they are the chief protein components of chromatin, acting as spool around which DNA winds•without histones, the unwound DNA in chromosomes would be too long•Slide 12•Slide 13•Slide 14•Structure of the nucleosome based on x-ray crystallography•A nucleosome consists of a protein core with DNA wound around its surface like thread on a spool•The core is an octamer containing 2 copies of each of histones H2A,H2B,H3, and H4•Nucleosomes contain 147 base pairs of DNA wrapped one and 2/3 turns around the protein core•Slide 15•Slide 16•Summary of post-translational modifications observed in human histones•Slide 17•Slide 18•a) model for the folding of a nucleosomal chain at top into a “zig-zag ribbon” of nucleosomes containing two “strands”.•In each ʻstrandʼ the nucleosomes are aligned with each other like a stack of coins•These 2 ʻstrandsʼ of nucleosomes are then wound into a left-handed double helix called a ʻtwo-startʼ helix•b)Model of 30-nm fiber based on x-ray crystallography•Slide 19•Slide 20•Nonhistone proteins provide a structural scaffold for long chromatin loops•Slide 21•Models of SMC proteins (Structural Maintenance of Chromosome proteins) complexes and their association with 30 n chromatin fibers in interphase cells•SMC proteins help maintain the structure of chromosomes•a) an SMC proteins complex consists of 2 monomers SMC2 (blue) and SMC4 (red), whose hinge domains associate•The head domains, which have ATPase activity, are linked by kleisin protein, forming a ringlike structure•**remember this is important later b/c something cleaves the kleisin ring in the cell cycle•b)the ringlike SMC complex topologically links 2 chromatin fibers (gray cylinders)•c) lops of transcriptionally active chromatin may be tethered at their base by several