The regulatory complex of Drosophila melanogaster 26S proteasomes. Subunit composition and localization of a deubiquitylating enzyme.
Drosophila melanogaster embryos are a source for homogeneous and stable 26S proteasomes suitable for structural studies. For biochemical characterization, purified 26S proteasomes were resolved by two-dimensional (2D) gel electrophoresis and subunits composing the regulatory complex (RC) were identified by amino acid sequencing and immunoblotting, before corresponding cDNAs were sequenced. 17 subunits from Drosophila RCs were found to have homologues in the yeast and human RCs. An additional subunit, p37A, not yet described in RCs of other organisms, is a member of the ubiquitin COOH-terminal hydrolase family (UCH). Analysis of EM images of 26S proteasomes-UCH-inhibitor complexes allowed for the first time to localize one of the RC's specific functions, deubiquitylating activity. The masses of 26S proteasomes with either one or two attached RCs were determined by scanning transmission EM (STEM), yielding a mass of 894 kD for a single RC. This value is in good agreement with the summed masses of the 18 identified RC subunits (932 kD), indicating that the number of subunits is complete.
Hölzl
H
H
Max-Planck-Institute of Biochemistry, D-82152 Martinsried, Germany.
Kapelari
B
B
Kellermann
J
J
Seemüller
E
E
Sümegi
M
M
Udvardy
A
A
Medalia
O
O
Sperling
J
J
Müller
S A
SA
Engel
A
A
Baumeister
W
W
D000818:Animals; D004331:Drosophila melanogaster / Q000201:enzymology*; D015180:Electrophoresis, Gel, Two-Dimensional; D004591:Electrophoresis, Polyacrylamide Gel; D004625:Embryo, Nonmammalian / Q000201:enzymology; D046911:Macromolecular Substances; D017348:Microscopy, Electron, Scanning Transmission; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010447:Peptide Hydrolases / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000648:ultrastructure; D046988:Proteasome Endopeptidase Complex; D017434:Protein Structure, Tertiary; D017422:Sequence Analysis, DNA; D020539:Sequence Analysis, Protein; D017386:Sequence Homology, Amino Acid; D013869:Thiolester Hydrolases / Q000235:genetics / Q000378:metabolism; D043222:Ubiquitin Thiolesterase; D014452:Ubiquitins / Q000378:metabolism*
D046911:Macromolecular Substances; D014452:Ubiquitins; D013869:Thiolester Hydrolases; D010447:Peptide Hydrolases; D043222:Ubiquitin Thiolesterase; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease