Часть 2 (1121000), страница 13
Текст из файла (страница 13)
r o 6 ue u r l u a u . r p l tul t D e a q l o 1 , i ; 1 q 6 rp1a 1 t o 1u r e 6 esr peaq urso(tuaq] ,al)b aqt +o pua aq] rV OlHlVltVpuas n1 ddav -1rupuaSnutulIr)oulsurmodIa ; t { >a a a ue + o! e } s a q } o } 6 u r u . r n l a t^qaraql 'dcv punoq slr sasolpeaq aq1 'a1or1s.rer'aoda q l ' o o s i n o )e q l u l u o r l e u l l o ; u o r1 e u r 6 r . sr o1 rs u l e 6 a lp e a q a q l q r r q m6 u u n p a d e q su r a 6 u e q t 6 u r l e t a u a 6 - a : . r o ;a q l - a ) o r l s i a M o d a q l s t a 6 6 u 1a s e a l a sJ t q tu r ] ) e o l p e a q a q l ] o 6 u t p u t ql q 6 ! f a q f q y n n{ 1 1 u e 1 r u .
r o > u o :'srs{lorpAq {q parnpotde l e q d s o q dl u e 6 l o u r a q 16tyl o a s e a l a sl a s n e )l u a u l e l t ]u t D e a q l u o a l t sM a u e o l p e a qurso{uraq11o 6urpurqleam y gNlIvUlN!19-l)UOlu r e l o r da q 1o 1 p u n o q { 1 g q 6 r 1u r e t u a rp a r n p o t d( d ) a l e q d s o r l dt r u e 6 t o u rp u e d C Va q ] l n q ' s r n ) ) o6 t y 1 o s r s f l o r p { Hu ] u S } n o q p } o a ) u e } s t pe , { q 1 u a u .
r e lar ;q } 6 u o l e p a t e l d s r pe q o } p e o q a q } s a s n e )1 e q 1a 6 u e q ra d e q sa 6 l e 1e 6 u u a 6 6 u 1 ' a l n ) a l o udl f va q ] p u n o r e l l a q su r e l )e e ) r l s a s o l )] + a l )a q f a l ) l f , o ftsrs^roua^HI( u r p e a L l lo 1 a s o l :i { l a ns u r e w a tr { l q e q o t dp e a q a q l A l r l e e tu l q 6 n o q l l e' a 6 u e q )s l . { ls a z l s e q d u t au r l r e p u e p e a q a q l u a a M l a qa l a q u M e l p a l e d sa q l )' t u a u r e l raj q l 6 u o 1 ee ^ o uol lr snnollpeue utpe lol peaqa q l ; o , { 1 r u r ; ; ea q } s a ) n p a ls t L l l a } t s6 u r p u r q - u r l >aeq }d n a ) e u l e q l s u t e u l o pa q l ] o u o t l p u t J o l u o a) ql ur a6ueqr] q 6 1 1es s a s n e :( ; a l e r p a t u L lpr u e ( ] u a u e l t l u t 1 r ea q lu r o J ]t s a q u n ] a p t sa q l u o ' s tl p q ] ) p e a q e q l + o , , ) ) e q , ,a q lu o g a p a 6 r e 1a q l o t s p u r qd 1 V ] o a l n ) a l o u rV O l S V l l : l UluauJelr] )ilrq]u IsoAurt_)eq],{qpa1eurura1Aprder u.,t:d"'t ii:#'#i:Ir""'ii"ffs r q t' a p s n u 6 u r p e .
r l u o t^ l a ^ t ] ) eu e u l ( q l e a p+ o A l t p i 6 uaq1'sr1towto6rLto1 a;qlsuodsatst lr asne)aqpoujeuo s ) u o l l e t n b t l u o tt o 6 u e u t ] u a u l e l t ]u r l t e u e o l u o , { ; 1 q 6 1 1 p u as nl dp a ) ) o l s ra p r l o e l ) n up u n o q e 6 u r 1 : e ;p e a q u r s o { u re'aln6r; srqt ut uMor]sap{raq1;o ue}s aq} }V O:ll{iVIfVIp e a qu r s o ^ upuasnu tLlturlleluaure||+LLOLsuolovuuflnfttoy\lIpr] sreqs!lqnduPllru)ewuorJ uorssruJaoqllM'866t '9 r8-€ [8:56€atnloN''P ]a ullqPs'lruoU) 'uorleluauoailsoddoaq]qlr/v\sraurlpsuloj'snururjal-Jaqlle ureuop iolot! aql ql!/vlroloulpal)arrp-pua-snutwe' \DItrloosotou! p)N palle))€ [-ursaur)(B)'dals'pua snld]xeu eql e)el ol pesrodalnqntor)r.ueql prpmol6urlurodsr peaqpunoqun'puo)osaql'(ar!s6urpurqaptloal)nuaqr u! dlv qtlM)alels alorls-lsode ur alnqnlor)r[!aql ol punoqsrrarurpaql Jo peeqauo uaq^'olnqnlor)rLUaql,o pua snloaqlpreMolsa^ou pue snuruilal-Ns/uraloroaql le ureuop rolor.l_rslrseq(ursaur)leuoltua^uol)[-ursour)(y)'({do>sor>rruuorlre;aoft> ^q peurLuralap)salnqnlor)rutol peq)ellPsraurpaql,o a6eur uorln;osa.rra/vlole oluo (,{qder6oq1e1s{rr{er-x {q peururalap)sraLurpuralord-Jolouraarj aqt Jo sarnl)nlls aql6ulug,{q palerauabararrnsa6eurasaLll'salnqnlor)!urol punoqsulalordI;ruepadns u!sou!Ipue -prervrJo,6ur1;em-prem1)eqJo uollelualrg 69-9 1 eln6;1(ureuroprolour)peoq(8)l!erllel(ureuroprolour) (V)peaq)N)Nrolou pepalp-pua snldl-ursaullrolor! paperp-pue snurur( p ) N ) €[ - u r s a u r lccoluaurelrloloro- alnqnlor)rtrip e a qu r s a u r lpunoqun-{ooq V '(16-9 arn8r4 aas) 9 Ja}dPqO uI pessncslp esPdIV slJe(uExeq eq} Joe^qeleJ xeldruoJ aJoru e eJoJaleql sl ]I luleluop pulluJal-J uIEI{J-,{^eeq aql snldsurBruopwvXIs :suleruop ue^as luo4 peruloJ 3uu ruueld e Jo slslsuos pBeq aql'ppeq pedBqs-8uu 'eleJoqeleue uJoJ ot pasn sI uIPq3.{,reaqaqtSo uonJod Jo[Euraq] alrqM'alnseloru uleu,{p eq} uI suIEqJ lrreaq raqlo eq} o} speuuof, pu€ suleq:)'luerue^olu aqt selEeJJlq311o ]as E spuq teql IIB] e sruJoJuoluod pupural-g slllPql ernlsnDs JrsEq eq] surroJ suolpp 000'009 uPql alolu Jo uleqs I^eaq 1uer3y'eBuEqJIEuollBIUJoJuooSulluJauaS-ac;o;e ol se ila^ sESurpurqun pue SuIpuIqapqnlorsrru 01 srs,ltlorp^q eppoelsnu eql SuIdnos Jo alnr [EJaueSeq] s,i\/\olloJ'sursauDlrololuuleudp eqlsIpelEleJundlprnpnrlspueolsulso^luilps ]nq' (tg-gl aJntIC) luelualoru JoloruJo dllpuorlcarpaq] saurruJelap,,(qaraqtpuE 'peeq puoces eql JoJ alts Sutputq ]xeu aql saselq'dalslxauaql loJ'urvroqsssa>ordeql;o teadarl)exoue,{qspaalotdqrtqnnpuestsfilotp{q(!d)aleqdsoqdaql'(esPalalpasrodursaurlrvrousraln)alourdcvtra)eJJnsalnqnlor)rurdfv sal|nballuaLuq)elap)punoq dCV tll!/vlalnqnlolllu, eql ulolJpeq)elapseqlt a)uo 'preMlo,uteirioploloLuleal aqr sllndUlqsslql'(llo)palro)poutmualutaLllpue uteutoprolou aql uaamlaqautl6utlleuuole se aroq umelp st lalutl lrau oql) uolleui.lo;uor6urlutod-plervuo;e uol; Urqsol,,le)utl))au,,aql pa1;eraptldad;1euse o16urlurod-premrearslql ul E pue ze sasne)ureuroprolor.ilsrqlol dIV,o 6urpu;qaql'(6utarretpureuop rolot! luolJ aql u! dCV loj dIV lo abueqrxaue ,{qs;eueduaerr,rlaq)prennrolaql'al!s 6u1pu;quanup srureuop rolou,rearaql,o luaula)eldsrpsr peeq6utpeello ]uol]sr!u! dov tlll/!{alnqnlol)ll.!aql ol punoq,(1asoo;'@aatbaql allqMijIV ol pue alnqnlor)lul aql ol punoq ,(llqbtl sl4top) peaq6ur66e1ro rearaql'speoqutsautloml aqlJo auo'dalsq)ea,o uels aql lV.l)el] sl! jo{;a1alduor }noql!/v\alnqntot)ttuaLlluo sa)ue}srp6uo; to; anouo6 6ur11a1'a1ts6u;putqsltll 6urs61ue) raurp ursautlaql 'uoltotu,,pueq-la^o-pueq,,ullnqnlelqelle^elxau aql ol spulqaluaql puP'uleuloplolol'ulaulleoaqt sassed'e1rs6utpurqutlnqnlsll ulolJsaq)elappeaqJealaq],'dals,,ursour)e 6uunplrauueu paleutptoo)e ul llom suleuloplolou, ulseulloml aql'(8S-91arnbrleas)lre]llo)-pallo)6uo; e q6nolql pal)auuo)oMl Jolauilp elolotu 6u1pu1q-ap;toel)nuale leql (speoq)suleLuopsr [-ursaur)<-LVVg>'ulsout>1o a;r(r ;erluaqrouetl)au aql 79-91 etn613uolalalsolr() eql :9 L raldeqf8 t0 tMOLECULARMOTORSI019AAA domains(B)AAA domainspower stroKe,8nmcADP + PrAAA domainsin motorheadmajor ATPase+C - t e r m i n adl o m a i nattachmento cargoo r a n o t h e rm i c r o t u b u l e(c)1 5n mshaped linker region connects the hear,y-chain tail to the AAA domain that ismost active as an ATPase.Between the fourth and fifth AAA domains is a heavychain domain that forms a long anti-parallel coiled-coil stalk.
This stalk extendsfrom the top of the ring, with an ATP hydrolysis-regulated microtubule-bindingsite at its tip. Dlmein's "power stroke" is driven by the release of ADP and inorganic phosphate, and it causesthe ring to rotate relative to the tail (Figure f 6-64).Although kinesin, myosin, and dynein all undergo analogous mechanochemical cycles, the exact nature of the coupling between the mechanical andchemical cycles differs in the three cases. For example, myosin without anynucleotide is tightly bound to its actin track, in a so-called "rigor" state, and it isreleased from this track by the association of ATP In contrast, kinesin forms arigor-like tight associationwith a microtubule when ATP is bound to the kinesin,and it is hydrolysis of AIP that promotes releaseof the motor from its track.
Themechanochemical cycle of dlmein is more similar to myosin than to kinesin, inthat nucleotide-free dynein is tightly bound to the microtubule and it is releasedby binding AIP However, for dynein the inorganic phosphate and ADP appearto be releasedat the same time, causing the conformational change driving thepower stroke, while for myosin the phosphate is released first and the powerstroke does not occur until the ADP subsequently dissociates from the motorhead.Thus, cytoskeletal motor proteins work in a manner highly analogous toGTP-binding proteins, except that in motor proteins the small protein conformational changes (a few tenths of a nanometer) associated with nucleotidehydrolysis are amplified by special protein domains-the lever arm in the caseof myosin, the linker in the case of kinesin, and the ring and stalk in the case ofdgrein-to generate large-scale (several nanometers) conformational changesthat move the motor proteins stepwise along their filament tracks.
The analogyFigure 16-64 The power stroke of dynein.(A)Theorganizationof the domainsin eachdyneinheavychain.Thisis a hugemolecule,containingnearly5000aminoacids.The numberof heavychainsin adyneinis equalto its numberof motorheads.(B)Dyneinc is a monomericflagellagreenalgadyneinfound in unicellularChIomydom onas reinhardtii.rhe largedyneinmotor headis a planarringdomain(gray)andcontaininga C-terminalsixAAAdomains,four of which retainATPbut only one of whichbindingsequences,(darkred)hasthe majorATPaseactivity.Extendingfrom the headarea long,coiledcoil stalkwith the microtubulebindingsiteat the tip, and a tail with a cargoattachmentsite.In the ATP-boundstate,the stalkis detachedfrom the microtubule,causesstalk-microtubulebut ATPhydrolysisreleaseof ADPSubsequentattachment.and Pithen leadsto a largeconformational"power stroke"involvingrotationof theheadand stalkrelativeto the tail.Eacha stepof about8 nm alongcyclegeneratesthe microtubuletowardsits minusend.(C)Electronmicrographsof purifieddyneinsin two differentconformationsrepresentingdifferentstepsin thecycle.(B,frommechanochemicalS.A.Burgesset al.,Noture421:715-718,from Macmillan2003.With permissionLtd.)Publishers1020Chapter16:TheCytoskeletonbetween the GTPasesand the cytoskeletal motor proteins has recently beenextended by the observation that one of the GTP-binding proteins-the bacterial elongation factor G-translates the chemical energy of GTP hydrolysis intodirectional movement of the mRNA molecule on the ribosome.MotorProteinKineticsAreAdaptedto CellFunctionsThe motor proteins in the myosin and kinesin superfamilies exhibit a remarkable diversity of motile properties, well beyond their choice of different polymertracks.
Most strikingly, a single dimer of kinesin-1 moves in a highly processiuefashion, traveling for hundreds of ATPasecycles along a microtubule withoutdissociating. Skeietal muscle myosin II, in contrast, cannot move processivelyand makes just one or a few steps along an actin filament before letting go.Thesedifferences are critical for the motors' various biological roles. A small numberof kinesin- I molecules must be able to transport an organelle all the way downa nerve cell axon, and therefore require a high level of processivity.Skeletalmuscle myosin, in contrast, never operates as a single molecule but rather as part ofa huge array of myosin II molecules in a thick filament.
![](https://s.studizba.com/z.php?f=/templates/si/i/noavatar.png&w=100&h=100&t=1"){kind=avatar}
