Non-enzymatic Protein Function (5/15) Flashcards
Cytoskeleton function
Shape and structure
Motion
Cell division
Organelle and biomolecule transport
Actin
forms the microfilaments of the cytoskeleton and is very abundent
Actin in microfilaments: function
motion
structure
cell division
muscle contraction
Individual actin monomers
G-actin because they have a globular shape and posses a site where ATP or ADP can bind
When a ton of G-actin bind together…
It forms F-actin which stands are filamentous actin and two of these stick together to form a microfilament
Rapid growth and disassembly
when polymerization= depolymerization, we have tread-milling and when we want to stop, we have capping proteins
Intermediate filaments
a long alpha-helical section
very flexible: can be stretched
Where are intermediate filaments found?
in the cytoplam
What is the main function of intermediate filaments?
structural support
cell adhesion
organelle positioning
Microtubules
structural support for cilia and eukaryotic flagella
chromosome separation during mitosis and meiosis
intracellular transport
Subunit of microtubules
tubulin dimer consisting of an alpha-tubulin and a beta-tubulin
bring GTP or GDP
Motor protein functions
transport
motility
muscle contraction
Kinesins
ATP-ases
consumes energy from ATP hydrolysis
Direction of kinesins
move to + end of microtubules which is to the periphery and this is called anterograde transport
Make up of kinesins
heterotretramers
made of of 4 subunits that are not all the same
2 subunits: heavy chains, with two head groups that are the feet
2 other subunits: light chains
How kinesins move
ATP binds head to the microtubule causing a conformational change and swing with other head bound to ADP forward (ADP has head be detacted)
Direction of dyneins
move to the cell center to the minus end and is called retrograde transport
Axonemal dyneins
found in cells with only cilia or flagellum
Cytoplasm dyneins
transport cargo for cell function
Myosins
ATP-ases
main job: muscle contraction
What myosins are composed of
head, neck, and tail domains
Cell adhesion molecules types
selectins, cadherins, integrins
Selectins
mediated inflammatory cells: platelets and endothelial cells
How selectins works
cytokines express selectins. luekocytes stick to selectins to slow them down and do reaction
Heterophilic and Ca2+ dependent
Cadherins
cell growth and development
calcium ions, span entire cell membrane, transmembrane
Integrins
adheres to extracellular matrix and cell signaling
location: cell membrane
Action: binds ligands and cations
Cell junctions
anchoring junctions
gap junctions
tight junctions
Anchoring junctions
connect cytoskeleton of one cell with the cytoskeleton of another or extracellular matrix
Adherens junction and desmosomes
types of anchoring junctions
Gap junctions
connexin which links the cytosol of neighboring cells. facilitates cell-to-cell communication
What can pass through gap junctions?
amino acids, vitamins, sugars, nucleotides, Ca2+, and cAMP
Tight junctions
in epithelial cells and do not allow anything but water and some ions
contain occludin and claudin
EX) blood brain barrier
Regions of an antibody
constant region, variable regions, and hypervariable regions (where antigens bind)
Isotypes of antibodies
different kinds of antibodies
IgA
in gut, blocks pathogens and respiratory tract
IgD
b cells
IgE
allergic and anti-parasitic immunity
IgM
early response
IgG
eliminates bacterial and viral pathogens (most common)- only ones to cross placental membrane
Class switching
b-cells and change isotypes by changing heavy change but keeping hypervariable region
