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MCB 104
What do MTs do?
Regulate cilia- Beating of cilia and flagella
Transort organelle
Mitosis
o !i"ides chro#oso#es$sindles
Microtu%les adot different organi&ations
'n different cell c(cle stages
Microtu%les are d(na#ic
Microtu%les are constantl( ro%ing out$going out and in
o The( are sa#ling and %ringing %ac) infor#ation of cell and
*hat+s going on
,roerties of #icrotu%ules the tu%lin heterodi#er
.u%unit tu%lin sta%le heterodi#er of alha-tu%ulin and
%eta-tu%ulin
Beta and alha loo) a li)e
Beta-tu%ulin can echange/h(drol(&e T, alha cannot
3lha %inds to T, irre"ersi%l( al*a(s %inds
Beta-tu%ulin %inds T, and can h(drol(&e it
,roerties of #icrotu%les
Microtu%le MT structure- a hollo* ol(#er of tu%ulin su%units
1 linear rotofila#ents
o end to end %( olari&ed %inding of heterodi#ers
o not sta%le
o sta%le *hen arranged in a tu%e
end to end and side to side %inding gi"es the #icrotu%ules
sta%ilit(
nonco"alent %inding
MTs are olar-su%units unifor#l( oriented alternating alha/%eta
%eta to*ard 7 end
7 end-fast gro*ing
- end- slo*er gro*ing
lateral interactions %et*een rotofila#ents for# tu%e of
#icrotu%ule
ol(#eri&ation )inetics si#ilar to actin
o Cc
o 8ucleation
o 9longation
o .tead( state
:ollo* tu%e- 26 n# dia#eter
MT asse#%l( is couled to T, h(drol(sis
T, tu%ulin adds to 7 ends T, then h(drol(&ed to !,
!oes it in a concentration deendent #atter
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Critical concentration- 3dding #ono#ers and losing #ono#ers at
the sa#e rate so #ass
sta(s sa#e
T, ca if tu%ulin greater than critical concentration gt ca-
sta%le structure
T, h(drol(sis desta%ili&es #icrotu%ules
;ose sta%ilit( *here rotofila#ents sta%ili&e each other
The rotofila#ents cur"e %ac)o Ma)es a #ore raid disasse#%l(
!isasse#%l( fro# 7 end
- end is anchored
eeling %ac) is called catastrohe *here reasse#%l( is called
rescue
Microtu%le d(na#ic insta%ilit( at stead( state
Microtu%les rare often anchored so indi"idual su%units generall(
sta( the sa#e at *here
the( are< ;ifeti#e of tu%ulin di#er in a resting cell is
rett( long
3t critical concentration MTs are constantl( gro*ing and
shrin)ing
The structural %asis of d(na#ic insta%ilit(
MCB rofessor e"a nogalesMicrotu%les are nucleated fro#
centroso#es
8ucleation re=uires tu%ulin and other things as *ell
8eed to add centroso#e
Centroso#e- acts as a MT>C- #icrotu%ule organi&ing
center
Microtu%le organi&ation in #a##alian cells
Centroso#es are found in right angles and found in a
ha&e
T*o centrioles #a)e u centroso#e
,-9B1
7 end trac)ing rotein sho*s gro*ing MTs
Microtu%les radiate out of centroso#es and are organi&ated
there
Microtu%le function in cells controlled %( %inding roteins
Microtu%le #otor roteins
MT ro"ide trac)s for cargo
Motor roteins 7 and @ end directed
o Ainesins
o !(nein
!i#ers *ith glo%ular head *hich %ind to 3T, and
h(drol(&es< Ta)es that associate *ith
cargo
Ainesin #echanis#
Wal) along cell
Microtu%le #otors in cell organi&ation
Melanoso#e ositioning
>rganelle
,ig#ent$in"ol"ed in ca#oflauge
3ctin and #icrotu%ule drugs
Can easil( get into cells and can interfere
.#all #olecules that associate *ith su%un it and affect
ol(#eri&ation
