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The Biophysical TheBiophysicalSociety

Society of of Japan Japan General General Incorporated IncorporatedAssociation Association

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2os7mf7y-AopestewaSexravaasutasth Crysta}structure of the yeast20S proteasomein complei new inhibitor

1PT104

report

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multi-catalytic

nonfunctional

selution

structure

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data were measured lseA comprises

compound and has functienfordegrades unfold proteins.The function of proteasome invo)ves ubiqutin role in livingorganism. We found a proteasome systern that plays irnportant new proteasome inhibitor thathas no side effect in norma] cell, but efTect foTthe the active-site tumor ce]1 degTadation,To reveal the precisestructure ofthe inhibitor-binding site and to obtain the fundamental date for development of more effective inhibitor foranticancer reagent, we have determined the crysta] structure ofthe IPTI074.1 yeast 20S proteasome incornplex with the inhibitor.

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the

ofIseA

cleterminedby NMR at RIKEN NMR

spectroscopy.

Facility.) The domain consisting ofthree a-helices, ene "hacksaw-like" 3to-helix and eight B-strands, which is a novel fold. A notewonhy region in the IseA structure is a flexibleloop between P4 and 3iohelix,which looks likea blade of a hacksaw. Electrostatic distributjon potential of IseA shows that most surface eharges the positivelybut the surface around loop region charges negative]y. In contrast, an active-site cleft of DLendopeptidase, LytF, is expected to charge NMR chemical shift positively. perturbationof IseA, interactingwith LytF, indicates that the petential interaction sites are locatedaround the loop region, the end region of a-helix, and C-terminal region. These results suggest that IseA inhibitsDLendopeptidase through directinteractien of the loop and around the region with structure

Takuma Maekawai Kazuya Nishio2, Bahrudin UdinS, Ichiro Hisatome3, Yasushi Saek i4, KeljiTanaka4,HiroshiYamaguchii, yukio Morimotoi (i Grad. 2Grad, Slrh. thi&Tlec, Uhiv. Kkengaku, Sch. Ph}'si,Uhiv. 1