考研資料北京大學(xué)細(xì)胞生物學(xué)-第十章節(jié)+細(xì)胞骨架(中)-

Basal

bodystructureC.

Characteristics

of

MTaasssseemmbbllyyDynamicinstability

duethe

structuraldifferencesbetween

a

growinand

a

shrinkingmicrotubule

end.GTP

cap;Catastrophe:accidental

lossGTP

cap;Rescue:

regainof

GTP

cap·

Why

the

centrosome

can

act

as

MTOCStructureNo

centriolesin

Plant

andfungi·

Experiments

supporting

thatcentrosome

is

the

MTOCTreat

cell

withcolcemidCytosolic

MTs

depoly,

except

those

in

centrosomeRemovecolcemidTublin

repolyExpla

I:

MTOC

nucleatepoly

of

tubulinsExpla

II:

MTOC

gatherMTs

in

cytosolB

centrosome+TubulinsMT+TubulinsNoA·MT

are

nucleated

by

a

protein

complexcontaining

-tubulinThe

centrosome

is

the

major

MTOC

of

animal

cells·

Drugs

affect

the

assembly

of

MTsColchicineBinding

to

tubulin

dimers,

prevent

MTspolymerizationTaxolBinding

to

MTs,

stabilize

MTsThese

compounds

are

called

antimitotic

drugs,

and

haapplication

in

medical

practice

as

anticancer

drugs·

Microtuble-associated

proteins(MAPs)MAPs

modulate

MT

structure,

assembly,and

functionKatanin

like

proteinsMAPsTau:

In

axon,

cause

MTs

to

form

tight

bundlesMAP2:

In

dendrites,

cause

MTs

to

form

looser

bundlesMAP1B:

In

both

axons

and

dendrites

to

form

crossbridgebetween

microtubulesControlorganizatioMAPsMAP1A,

MAP1B,

MAP1CMAP2,

MAP2cMAP3，MAP4TauThe

importance

of

MAPs

for

neurite

formationOrganization

of

MT

bundles

by

MAPs

.Spacingof

MTs

depends

on

MAPsInsect

cell

expressiIngsect

cell

expressingMAP2

tauFrom

J.

Chen

et

al.

1992.

Nature

360:

674The

effects

of

proteins

that

bind

to

MT

ends(A)The

transitibetween

Mtgrowth

and

Mtshrinking

iscontrolled

in

cby

specialproteins.(B)Cappingproteins

help

tlocalize

Mt

inbudding

yeastcell.5.

Functions

ofMTs1.

Maintain

cell

shapeFig.

10-31

Microtubule

dynamics

in

a

living

cell.

A

fibroblast

was

injwith

tubulin

that

had

been

covalently

linked

to

rhodamine,

so

that

approxim1

tubulin

subunit

in

10

in

the

cell

was

labeled

with

a

fluorescent

dye.

Noteexample,

that

microtubule

#1

first

grows

and

then

shrinks

rapidly,

whereasmicrotubule

#4

grows

continuously.

(P.J.

Sammak

et

al.,

Nature

332:

724-73細(xì)胞內(nèi)物質(zhì)運(yùn)輸Motor

ProteinKinesin

FamilyDynein

Family染色體運(yùn)動Intermediate

filaments,IFsIFs

are

the

most

abundant

andstable

components

of

thecytoskeletonFigure

10-13

The

domain

organization

of

intermediate

filamprotein

monomers. Most

intermediate

filament

proteins

shasimilar

rod

domain

that

is

usually

about

310

amino

acids

longforms

an

extended

alpha

helix.

The

amino-terminal

and

carboxyterminal

domains

are

non-alpha-helical

and

vary

greatly

in

siand

sequence

in

different

intermediate

filaments.Figure

10-14.

A

current

model

of

intermediate

filamentconstruction.Figure

10

–16.

Electron

micrographs

of

two

types

of

intermediatefilaments

in

cells

of

the

nervous

system.

(A)

Freeze-etch

image

ofneurofilaments

in

a

nerve

cell

axon,

showing

the

extensive

cross-linkingthrough

protein

cross-bridges

.

(B)

Freeze-etch

image

of

glial

filaments

icells

illustrating

that

these

filaments

are

smooth

and

have

few

cross-bridConventional

electron

micrograph

of

a

cross-section

of

an

axon

showing