Any slide that has no information for it was either self explanatory or had no additional information in the book Exam 4 Lecture 29 Video microscopy shows agellar movements that propel sperm and Chlamydomonas forward Slide 17 Slide 18 Slide 19 Slide 20 Slide 21 Slide 22 Slide 23 Slide 1 Slide 2 Slide 3 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 agellum Lecture 30 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 MT s 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 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 Organelle transport by MT motors Slide 4 Slide 5 Slide 6 previous slide set remember the basal body is an organelle formed from a centriole and a short It is found at the base of the cilium or agellum and serves as the nucleation site cylindrical array of MT s for the growth of the axoneme MT s structural organization of cilia and agella Slide 7 Slide 8 with ATP Electron micrograph of 2 doublet MTs in a protease treated axoneme incubated 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 Intermediate laments IFs are unpolarized have no motors Slide 10 Slide 11 Slide 12 Structure and assembly of intermediate laments a IF proteins form paralell dimers b a tetramer is formed by antiparallel staggered aggregation side by side of 2 c tetramers aggregate end to end and laterally into a proto bril identical dimers Slide 13 Slide 14 Keratin IFs are dynamic as soluble keratin is incorporated into laments Monomeric type 1 keratin was puri ed 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 laments 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 membrane Lecture 31 previous slide set Slide 1 Slide 2 Slide 3 Slide 4 Slide 5 Slide 6 Remember all eukaryotic cells nuclear envelope is a double lipid bilayer that encloses the genetic material in 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 dark staining areas in the Nucleus N outside the nucleolus n are heterochromatin The light staining whitish areas are euchromatin 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 During interphase human chromosomes remain in speci c territories in the 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 7 Slide 8 Slide 9 nucleus Slide 10 Slide 11 Slide 12 Slide 13 Slide 14 Structure of the nucleosome based on x ray crystallography thread on a spool the protein core H4 Slide 15 Slide 16 Slide 17 Slide 18 A nucleosome consists of a protein core with DNA wound around its surface like The core is an octamer containing 2 copies of each of histones H2A H2B H3 and Nucleosomes contain 147 base pairs of DNA wrapped one and 2 3 turns around Summary of post translational modi cations observed in human histones a model for the folding of a nucleosomal chain at top into a zig zag ribbon of nucleosomes containing two strands In each strand the nucleosomes are aligned with each other like a stack of coins These 2 strands of nucleosomes are then wound into a left handed double helix called a two start helix b Model of 30 nm ber based on x ray crystallography Slide 19 Slide 20 Slide 21 Nonhistone proteins provide a structural scaffold for long chromatin loops Models of SMC proteins Structural Maintenance of Chromosome proteins complexes and their association with 30 n chromatin bers 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 cell cycle remember this is important later b c something cleaves the kleisin ring in the b the ringlike SMC complex topologically links 2 chromatin bers gray cylinders c lops of transcriptionally active chromatin may be tethered at their base by several SMC complexes forming a topological knot in lecture 32 we ll discuss speci cally how the sister chromatids separate centromere refers to the dna sequence that represents the primary constriction Lecture 32 In the picture each chromosome has replicated and comprises 2 chromatids each containing one of 2 identical DNA molecules The centromere