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Kuliah Biologi Selbab sitoskeletonoleh Dr.Achamad Farajallah
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FILAMEN MIKRO
form a band just beneath the plasma membrane that
provides mechanical strength to the cell
links transmembrane proteins (e.g., cell surface
receptors) to cytoplasmic proteins
anchors the centrosomes at opposite poles of the cell
during mitosis
pinches dividing animal cells apart during cytokinesis
generate cytoplasmic streaming in some cells
generate locomotion in cells such as white blood cells
and the amoeba
interact with myosin ("thick") filaments in skeletal muscle
fibers to provide the force of muscular contraction
Fungsi-fungsi filamen mikro
awalnya dianggap berfungsi pasif
Porter 1976: mf terlibat dalam sistem transpor sitoplasma
Studi lebih lanjut: terlibat dalam banyak hal yang
berkenaan dengan fungsi aktif (mis. aktin miosin otot)
Struktur 3D hanya bisa dilihat dalam sel utuh/sayatan
tebal, termasuk dalam sel-sel non-otot
sampai saat ini hanya diidentifikasi dalam sel-sel eukariot
berdasarkan ukurannya:
filamen aktin (cell contraction & movement)
filamen intermediet: neurofilamen, tonofilamen,
prekeratin-filamen, dll (regulate the cell shape?)
FILAMEN MIKRO
FILAMEN MIKRO
Komponen penyusun: protein aktin
G-aktin – globular actin: monomer
F-aktin – filament actin: polymer
FILAMEN MIKRO
+ protein asesoris beragam bentuk & fungsi:
muscle specific actin: α-actin
non-muscle actin:
β-actin: ujung-
ujung apikal sel
-actin: basal &
lateral sel
actin-related protein
(Arp): pembentukan
inti filamen,
terutama pada sel-
sel bermigrasi
FILAMEN MIKRO
+ actin-binding proteins: mengatur interaksi antar filamen,
misal: miosin II dalam struktur miofibril
FILAMEN MIKRO – decorating actin MF
MICROFILAMENT – micovillus structure
FILAMEN MIKRO – struktur 3 dimensi oleh dimer filamen
FILAMEN MIKRO – branched actin networks
frog keratocyte cell: deep
etch TEM
actin monomer was
fluorescently labelled
the antibody attached
to gold particles
FILAMEN MIKRO – branched actin networks
FILAMEN MIKRO
FILAMEN MIKRO: miofibril
myoblas sinsitium sel otot fungsional
dalam sel otot fungsional: bundel-bundel miofibril
satu bundel miofibril : filamen tipis (dominan aktin),
filamen tebal (dominan miosin) & berbagai protein
asesoris memunculkan pita-pita terang & gelap
FILAMEN INTERMEDIET
ukuran 8-12 nm: antara tubulus mikro dan filamen mikro
deskripsi awal: antara aktin dan miosin
paling stabil dalam struktur polimer: that they serve as a
scaffold to support the entire cytoskeletal framework
mis.: neurofilamen, tonofilamen, prekeratin-filamen, dll
(regulate the cell shape?)
FILAMEN INTERMEDIET
(hanya) ditemukan pada organisme multisel
Protein fibrosa (bukan globular) dengan beragam
bentuk, struktur dan komponen penyusun:
I. Acidic cytokeratins – epitel
II. Basic cytokeratins - epitel
III. Vimentin – fiboblas, mesenkim, sel lensa mata
Desmin – otot (terutama otot polos)
GFA protein – sel-sel glial (terutama astrosit)
IV. Neurofilamen proteins – syaraf pusat dan tepi
V. Nuclear lamin – semua jenis sel multiselular
VI. Nestin – neuronal stem cells
IF typing serve as diagnostic tool, esp in metastasis stage of
cancer
FILAMEN INTERMEDIET
I II III IV V
FILAMEN INTERMEDIET
dimer tetramer protofilamen IF