Transcript MICROFILAMENTS AND INTERMEDIATE FILAMENTS

MICROFILAMENTS AND
INTERMEDIATE FILAMENTS
BY
PRIANKA RAJAN
Microfilaments and intermediate
filaments
CYTOSKELETOL COMPONENTS
• THE MAJOR FILAMENTS RESPOSIBLE FOR MUSCLE
MOVEMENT ARE ACTIN AND MYOSIN .
• THE ACTIN AND CYTOSKELETON MACHINARY IS
RESPONSIBLE FOR MAINTAINING CELL SHAPE AND
GENERATING FORCE FOR MOVEMENTS.
• POLYMERIZATION AND DEPOLYMERIZATION OF ACTIN
FILAMENTS
• 1.DRIVES THE MEMBRANE FORWARD.
• 2.SUPPORT OVERALL CELL SHAPE.
ACTIN STRUCTURE
•
THE ACTIN CYTOSKELETON IS ORGANIZED INTO VARIOUS LARGE
STRUCTURES THAT EXTEND THROUGHOUT THE CELL.
•
IT IS THE MOST ABUNDANT INTRACELLULAR PROTEIN IN MOST
EUKARYOTIC CELLS.
•
IN MUSCLE CELLS ACTIN COMPRISES 10% WEIGHT OF THE TOTAL
PROTEIN.
•
ACTIN EXISTS AS A GLOBULAR MONOMER CALLED G-ACTIN AND AS
•
A FILAMENTOUS POLYMER CALLED F-ACTIN.
•
EACH ACTIN MOLECULE CONTAINS A MAGNESIUM ION COMPLEXED
•
•
ACTIN FILAMENTS ARE POLARIZED WITH ONE END AND
CONTAINING AN EXPOSED ATP-BINDING SITE
MYOSIN
•
EIGHT MEBERS OF MYSOIN GENE FAMILY HAVE BEEN IDENTIFIED
•
MYOSIN I,II, AND V PRESENT EUKARYOTIC CELLS.MYOSIN VI,VII AND
XV HAVE FUNCTIONS ASSOCIATED WITH HEARING AND HAIR CELL
STRUCTURE.
•
INTERACTIONS BETWEEN MYOSIN II AND ACTIN FILAMENTS ARE
RESPONSIBLE FOR MUSCLE CONTRACTION.
•
CELL MOVEMENTS OTHER THAN MUSCLE CONTRACTION AND
CYTOKINESIS ARE BROUGHT ABOUT BY MYOSIN ISOFORMS –
KENESIN OR DYNEIN OR BY ACTIN POLYMERIZATION.
•
THIS INCLUDES MOVEMENTS LIKE VESICLE
TRANSPORT,MEMBRANE EXTENSION, CHROMOSOMAL MOVEMENT
ETC.
•
ALL MYSOINS CONSIST OF ONE OR TWO HEAVY CHAINS AND
SEVERAL LIGHT CHAINS THAT HAVE A REGULATORY FUNCTION.
CONTD…..
•
A CHARACTERISTIC HEAD,NECK AND TAIL DOMAIN IS FOUND
IN ALL MYOSIN HEAVY CHAINS.
• ALL MYOSIN HEAD DOMAINS HAVE ATPase ACTIVITY AND IN
CONJUCTION WITH THE NECK DOMAIN COUPLE ATP
HYDROLYSIS FOR MUSCLE MOVEMENT.
MUSCLE CONTRACTIONS
•
IN SKELTOL CELLS,ACTIN THIN FILAMENTS AND MYOSIN
THCIK FILAMENTS ARE ORGANIZED INTO HIGHLY ORDERED
STRUCTURES CALLED SARCOMERES.
• THE RAPID RISE IN CYTOSOLIC CALCIUM INDUCED BY NERVE
STIMULATION OF A SKELTOL MUSCLE CHANGES THE
INTERACTION BETWEEN ACTIN FILAMENTS AND
TROPOMYOSIN,EXPOSING THE MYOSIN BINDING SITES AND
THUS PERMITTING CONTRACTION TO OCCUR.
INTERMEDIATE FILAMENTS
• INTERMEDIATE FILAMENTS ARE FOUND IN NEARLY ALL
ANIMALS.
• THEIR PRINCIPLE FUCNTION IS STRUCTURAL.THEY PROVIDE
MECHANICAL SUPPORT FOR THE PLASMA MEMBRANE.
• THEY DISTRIBUTE TENSILE FORCES ACROSS CELLS IN A
TISSUE.
• MAJOR DEGENREATIVE DISEASES OF SKIN,MUSCLE AND
NEURONS ARE CAUSED BY DISRUPTION OF THE IF
CYTOSKELETON.
ARRANGEMENT OF ACTIN
ATP BINDING TO ACTIN AND
MYOSIN FIBRES
CONCLUSION
• THE EUKARYOTIC CELL CONTAINS THREE TYPES OF
FILAMENTS-ACTIN FILAMENTS(MICROFILAMENTS) ,
MICROTUBULES AND INTERMEDIATE FILAMENTS
• THESE MAKE UP THE CYTOSKELKETON.
• ACTIN AND MYOSIN ARE ORGANISED INTO HIGHLY ORDERED
STRUCTURES CALLED SARCOMERES.
• NERVOUS STIMULATION OF SKELETOL MUSCLES CHANGES
THE INTERACTION BETWEEN ACTIN FILAMENTS AND
TROPOMYOSIN , THUS EXPOSING THE MYOSIN BINDING
SITES FOR CONTRACTION TO OCCUR.
• INTERMEDIATE FILAMENTS PROVIDE MECHANICAL SUPPORT
FOR THE PLASMA MEMBRANE
THANK YOU!