Assembly of the eukaryotic 20S proteasome is an ordered process involving several proteins operating as proteasome assembly factors including PAC1-PAC2 but archaeal 20S proteasome subunits can spontaneously assemble into an active cylindrical architecture. Recent bioinformatic analysis identified archaeal PAC1-PAC2 homologs PbaA and PbaB. However, it remains unclear whether such assembly factor-like proteins play an indispensable role in orchestration of proteasome subunits in archaea. We revealed that PbaB forms a homotetramer and exerts a dual function as an ATP-independent proteasome activator and a molecular chaperone through its tentacle-like C-terminal segments. Our findings provide insights into molecular evolution relationships between proteasome activators and assembly factors.

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proteasome assembly factors molecular chaperone assembly factorlike proteins orchestration of proteasome subunits evolution atpindependent proteasome activator

Koichi Kato,Kentaro Kumoi,Tadashi Satoh,Kazuyoshi Murata,Takeshi Hiromoto,Tsunehiro Mizushima,Yukiko Kamiya,Masanori Noda,Susumu Uchiyama,Hirokazu Yagi,.An archaeal homolog of proteasome assembly factor functions as a proteasome activator.. 8 (3),.

Koichi Kato,Kentaro Kumoi,Tadashi Satoh,Kazuyoshi Murata,Takeshi Hiromoto,Tsunehiro Mizushima,Yukiko Kamiya,Masanori Noda,Susumu Uchiyama,Hirokazu Yagi,"An archaeal homolog of proteasome assembly factor functions as a proteasome activator." 8

Koichi Kato,Kentaro Kumoi,Tadashi Satoh,Kazuyoshi Murata,Takeshi Hiromoto,Tsunehiro Mizushima,Yukiko Kamiya,Masanori Noda,Susumu Uchiyama,Hirokazu Yagi,"An archaeal homolog of proteasome assembly factor functions as a proteasome activator."