ECM 2 Flashcards
(115 cards)
1
Q
Intermediate filaments:
differences with other cytoskeletal elements
A
polymers of 10nm diameter between microfilaments and microtubuels
encoded in genome by 70 different genes
tissue specific manner/NOT polarized
2
Q
Intermediate filaments:
is dimer form polarized?
A
Yes, IF proteins have N and C terminal domains. they are different.
3
Q
Intermediate filaments:
three parts
A
N terminal
C terminal
Rod: alpha helix in coiled coil domain by heptad repeat.
4
Q
Intermediate filaments - rod section. where are hydrophobic residue?
A
at position 1 and 4. helices of two proteins pack together, mediated by interactions between these hydrophobic side chains.
5
Q
Intermediate filaments: is tetramers polarized?
A
No, tetramers are symmetric. they are basic building block of IFs
6
Q
IF dimer is associate with other dimer in what fashion?
A
anti-parallel fashion forming tetramer
7
Q
IF tetramers are offset so what happens?
A
C-terminal ends overhang
8
Q
IF: tetramers assemble end to end and forming what?
A
protofilament
9
Q
IF: 4 protofilaments assemble into what?
A
protofibril
10
Q
IF: 4 protofibrils assemble into what?
A
10 nm of IF
11
Q
how many protofilaments IF contains?
A
16 protofilaments, interlocked
12
Q
IF stabler than what?
A
stable than microfilaments or microtubules, but still dynamic
13
Q
name of class 1 IFs?
A
acidic keratins at epithelial cells for tissue strength and integrity
14
Q
name of class 2 IF?
A
basic keratins at epithelial for tissue strength and integrity.
15
Q
name of type 3 IF?
A
Desmin, GFAP, vimentin at muscle, glial cells, mesenchymal cells for sarcomere organization and integrity.
16
Q
type 4 IF?
A
neurofilaments (NFL, NFM, NFH) at neurons for axon organization
17
Q
type 5 IF?
A
lamins at nucleus for nuclear structure and organization
18
Q
What are IF related diseases?
A
Epidermolysis bullosa simplex (EBS)
Hutchinson-guilford progeria caused by LMNA
19
Q
name of If at basal party ( inside) which forms heterodimer with other. Assemble into protofilaments
A
Keratin 14 / 4
20
Q
As cell mature, keratin 4/14 are replaced by?
A
keratin 1/10
21
Q
What cause EBS?
A
K14 lacking N or C terminal domain that forms heterodimers with K4. heterodimers cannot form tetramers and assemble into protofilaments.
Absence of K14/4 protofilaments, epidermis is separated from dermis (blister)
22
Q
cause of Hutchinson-guilford progeris?
A
mutations in LMNA
mutation in single base change that activates a cryptic splice site and produces a truncated lamin A protein (progerin)
23
Q
symptom of Hutchinson
A
premature aging craniofacial defects life expectancy 13-14yrs abnormal nuclear membrane tissues with high level of stress
24
Q
Lamin A is modified by what?
A
Farnesyl group (lipid)
25
what is farnesylated?
Ras
26
what enzyme cleaves precursor at site of farnesylation?
Ras converting enzyme (Rce)
27
what happened in mutant LMNA? (related to last step)
Last step is blocked in HGPS.
| intermediate accumulates in nuclei and deforms them.
28
This has been identified as part of screens to treat cancer?
FTI
29
If block farneylation of precursor protein, do you prevent disease symtopm?
yes.
researchers found that FTI not only prevented cardiovascular damage in young mice, but also reversed the disease in older animals treated after the onset of arterial damage.
30
Epithelial cells are polarized?
yes.
31
what is expanded at apical surface?
microvilli (actin based structures, not to be confused with cilia, flagella)
32
what contacts basal lamina?
basal surface
33
structure of basal lamina?
very thin, tough flexible sheet ( 60-120nm)
| forms a foundation on which columnar epithelia rest. in muscle or fat, basal lamina surrounds each cell
34
what are 4 roles of basal lamina?
1. tissue organizatino into distint compartment
2. tissue function
3. tissue repair
4. cell migration
35
what is basal lamina made of?
1. type 4 collagen
2. laminins,
3. perlecan
4. nidogen
36
what forms sheet of basal lamina?
type 4 collagen which associates with certain integral membrane protein
more than 20 types of collagen
37
what kind of proteins are collagens?
trimeric proteins made from three polypeptides, called collagen alpha chains. forms triple helix.
38
what is collagens' peptide sequence?
Gly X Y
| each chain form left-handed helix
39
on sequence Gly X Y, what are X Y?
often proline and hydroxyproline less frequently lysine or hydroxylysine
gly has small side chain (only a proton) is only one small enough to fit in center of triple helix. mutations in which othe raa replace gly, larger side chains destablize triple helix
40
each collagen chain forms what kind of helix?
left handed helix.
41
collagen: three chains wrap around each other to form what kind of helix?
right handed triple helix
42
what bonds hold 3 chains of collagen together?
Hbond
43
what holds proline ring in conformation, stabilizing collagen triple helix?
hydroxyl group in hydroxyproline
44
what are not compatible with standard alpha helix, but stabilize three stranded collagen helix?
proline and hydroxyproline
45
structure of type 4 collagen
trimeric molecules with rodlike and globular domains that form 2D network
small globular domain at N
large gobular domain at C
46
collagen monomers associate what manner?
tail - tail and head - head
47
in collagen, what occur between some C terminal globular domains?
covalent crosslinkning
48
what kind of interaction occur between monomers?
lateral interaction
49
what are associate to form lattice? (collagen)
dimers and tetramers
50
what are the collagen diseases
scurvy
alport syndrom
brittle bond disease
51
mutations in genes encoding collagen alpha 1 and 2 lead to what disease?
osteogenesis imperfecta, or brittle bone disease
mutations in gly forms unstable triple helices. only one mutant chain can distrupt triple helix!!
52
vitamin C ?
essential cofactor for enzymes that modify proline and lysine on type 4 collagen and other collagens.
53
what happen with deprived vit C?
prochains are not hydroxylated, and stable striple helices do not form. without support of collagen, blood vessels, tendons and skin become fragile
54
what is the alport syndroM?
progressive loss of kidney function (blood in urin)
| hearing loss due to inner ear defects, misshapen lenses.
55
80 % cases of alport syndroms caused by defects in what genes?
COL4A5 (Xlinked)
| autosomal mutations in COL4A3 and COL4A4
56
what happened in collagen 2 mutants?
shortened and deformed bones (dwarfism)
perlecan null embroys are more severely affected
57
where is fibronectin usually present?
on normal fibroblast, which adhere rightly TC dishes, but absent from surface of cancerous fibroblasts, which do not adhere
58
FN is essential for what?
cell migration, differentiation of many cell types and wound healing ( promoting clotting and migration of macrophages and other immune cells to wound site)
59
structure of fibronectin
dimer of two long polypeptide chains, linked by disulfide bond at C terminus
each chain is 60-70nm long and 2-3nm think
60
fibronectin : 3 types of repeating sequence?
1 repeat binds fibrin and heparan sulfate
2 binds collagen
3 repeats mediate contact with cells (90 aa and occurs 15 times in each subunit)
61
fibronectin connects to cytoskeleton via what?
focal adhesions
62
what is point of contact between cell and surface (ECM or tissue culture plate)
focal adhesion
63
type 3FN repeats contain what repeat?
RGD (Arg-Gly-Asp)
64
what are soluble forms of FN
circulate blood and function in clotting
65
insoluble FN?
assembles into fibrils only on surface or cells and only on cells that can bind to FN
66
FN accumulate initially like what?
as small dot like aggregates at focal adhesions (site of anchorage of actin filaments)
67
unlike collagen FN forms fibrils only when?
when present on cell surface
68
where is RGD sequence located?
at apex of loop that protrudes outward from molecule. and is sufficient to mediate adhesion to cells
69
molecular structure of the focal adhesion:
integrins in Ca rich medium similar to extracellular fluid, but no ligand, they appear bent ( inactive)
70
what cause outside-in activation?
presence of RGD, integrins change shape
intracellular domains of two subunits separate and expose binding site for talin on beta subunit.
binding tulin --> assembly of actin filaments anchored to integrin.
so when extracellular domain binds ligand, cytoskeleton exerts tension
71
what cause inside-out activation?
triggered by regulatory molecules, PIP2 (activates talins so increase affinity for beta subunit)
talin can compete with alpha for beta subunit. if talin binds, it forces integrins to open configuration.
72
skeletal muscle consists of fibers made of what kind of cell?
multinucleated cell
73
what links ECM to cytoskeleton in muscle cell?
dystrophin glycoprotein complex
74
during muscle contraction, increase in calcium level triggers what?
activation of NOS, producing NO and NO diffuses to blood vessels and relaxing smooth muscle.
increase blood flow to muscle tissue
75
sarcomeres consist of?
alternating filaments of actin and myosin.
76
what disk is darK?
z disc within I band.
77
sarcomere is consist of what kind of band?
A band and I band
78
A band has what
consists of bipolar myosin thick filament
79
I band?
actin fialment
80
what is polarity at z disk?
+
81
what powers movement along actin filament?
myosin
82
what is the first molecular motor idnetified, from skeletal muscle? this has globular heads at N
myosin2
83
myosin 2 is composed of ?
head neck and tail
84
thick filament of skeletal muscle can be dissolved in what kind of solution?
ATP and high salt
85
soluble myosin contains how many polypepetides?
6 polypeptides (2 heavy and 4 light chains)
86
2 light chains associated with what region?
neck region of each heavy chain
87
soluble myosin has what kind of activity?
ATPase activity
88
what cleaves myosin into two fragments? (HMM and LMM)
chymotrypsin (disgestive enzyme produced by pancreas)
89
HMM can further cleaved by protease papain into what?
Subfragment 1 (S1) and S2
90
S1 contains what?
head and neck
91
S2?
LMM comprised tail
92
what resides in the S1 fragment as does actin binding ability?
Intrinsic ATPase activity
| actin-activated ATPase activity
93
ATPase activity is enhanced by presence of what?
F-actin
94
using in vitro sliding filament assay, what is moving actin?
HMM and S1
95
increasing neck length of myosin does what?
the bigger steps taken by myosin and the faster it myosin on actin filaments
96
what forms a large gene family of acin-based motor proteins?
myosin
97
what typese of myosin are widely distributed among eukaryotes?
type 1 2 and 5
98
what type of myosin contains an insert in the head domain that causes it to work in the opposite direction ( towards - ends)
type 6
99
type 6 myosin invovled what kind of process?
endocytosis to move endocytic vesicles away from PM.
100
all membrane associated actin filaments have what kind of polarity?
(+) end pointed toward PM
101
TYPE 5 myosin
organelle transport
102
only class with a single head
type 1 myosin
103
class that has bind specific receptors on organelle and are involved in organelle transport?
type 5 myosin
104
type 2?
contraction with coil/coil tail
105
this type is unique in that it forms bipolar filaments. coiled coil tails interact with tails from other myosin molecules, forming bundles of myosin, with heads pointing outward.
type 2 myosin
106
what are budles that bipolar?
thick filaments
107
this type forms bundels in skeletal muscle
type 2 myosin
108
what kind of technique measure very small force?
optical trap
109
how does myosin 2 move along actin filament?
does not continuously interact with actin filaments, thus this type 2 binds, moves, and releases. "non-processive motor"
110
myosin 2 spends only how many %of each ATPase cycle?
10percent
111
duty raio of myosin 2 is what?
10%
112
type 2, so ___% of heads are engaged to provide smooth contraction
10
113
this type takes large steps, of 36nm length.
myosin 5
114
myosin 5 is ____motor?
processive motor
115
myosin 5 is in contact with filament for ___% of ATPase cycle (duty ration of myosin)
70
