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Manole A., Duca M.

Components and role of E3 into the Ubiquitin proteasome Pathway of Arabidopsis Thaliana

The University of Academy of Sciences of Moldova

3/2, Academiei Street, MD-202, !hisina", #ep"blic of Moldovae-mail$ ale%ander2&manole'(mail)com 

Proteasome are protein complexes specific to all archaea and eukaryotes. It plays an importantrole in the process of protein degradation which in some cases are the misfolded proteins or when their 

concentration is bigger than a normal one and of course and many other cases. In Arabidopsis th. more

than !"## genes encode the ubiquitin$%&' proteasome (U)$%&'* pathway ('malle and +ierstra %##"*.,pproximately !3## of these genes encode subunits of the E3 ubiquitin ligases which confer substrate

specificity to the pathway. -wo of the primary obecti/es in the field are to collect all specific genes

that encode proteasome classifying them by each complex group and Id gene and to run all this datato such programs as circus and cytoscape for analysis and /isuali0ation of proteasome biological

network especially pathways interactions and similarity of the E3 ubiquitin ligases. -his re/iew will

discuss how the Ub$%&' proteasome affects plant de/elopment by focusing primarily on the action of 

the E3 ubiquitin ligases.-he importance of the ubiquitin proteasome pathway to cellular regulation in eukaryotes has

 become increasingly apparent during the last se/eral years. In plants regulated protein degradation by

the ubiquitin$%&' proteasome contributes significantly to de/elopment by affecting a wide range of  processes including embryogenesis hormone signaling and senescence. ,lthough regulation of the

 pathway is complex its early steps can be described in a simply way. -he proteins are tagged for 

degradation with a small 1&2aminoacid ubiquitin protein (Ub* which is attached to that substratethrough the catalytic action of three en0ymes the ubiquitin acti/ating E! ubiquitin conugating

en0yme E% and ubiquitin protein ligase E3. -he result is a polyubiquitin chain that is bound to the

 proteasome allowing it to degrade the tagged protein (4odish 5. berk ,. et al), 20*+*. -he C terminus

of Ub forms a thioester bond with the E! in an ,-P 6dependent manner and transfers the acti/ated U)to an E% en0yme. -he e% either transfers ubiquitin directly to the E3 in the case of 5EC- (for 

homology to E&2,P C terminus* E3s or binds the E3 and transfers the ubiquitin to the substrate. In

either case the E3 en0yme specifies the substrate. -ypically this process is repeated se/eral times toattach multiple ubiquitin molecules to the substrate and polyubiquination has been shown to be

necessary for degradation of the substrate by the %&' proteasome (7ilkinson %###8 9oherty et al.

%##%8 :oon et al. %##"*. 5owe/er E3 ubiquitin ligases consist from a large and di/erse family of  proteins or protein complexes containing either a 5EC- domain or a ;Ine of 

the largest complex is Cyclin ? proteins (? 6 box* which contains more than 1## number of genes and

 plays an important role in such biological process as self incompatibility. ,nd E3 consist also frommany other small groups as CU44I

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makes us think that soon e/ery plant de/elopmental biologist will ha/e their fa/orite ?2box or ;I