Structural basis for Ca2+-independence and activation by homodimerization of tomato subtilase 3.
Subtilases are serine proteases found in Archae, Bacteria, yeasts, and higher eukaryotes. Plants possess many more of these subtilisin-like endopeptidases than animals, e.g., 56 identified genes in Arabidopsis compared with only 9 in humans, indicating important roles for subtilases in plant biology. We report the first structure of a plant subtilase, SBT3 from tomato, in the active apo form and complexed with a chloromethylketone (cmk) inhibitor. The domain architecture comprises an N-terminal protease domain displaying a 132 aa protease-associated (PA) domain insertion and a C-terminal seven-stranded jelly-roll fibronectin (Fn) III-like domain. We present the first structural evidence for an explicit function of PA domains in proteases revealing a vital role in the homo-dimerization of SBT3 and in enzyme activation. Although Ca(2+)-binding sites are conserved and critical for stability in other subtilases, SBT3 was found to be Ca(2+)-free and its thermo stability is Ca(2+)-independent.
Ottmann
Christian
C
Chemical Genomics Centre, Otto-Hahn-Strasse 15, 44227 Dortmund, Germany.
Rose
Rolf
R
Huttenlocher
Franziska
F
Cedzich
Anna
A
Hauske
Patrick
P
Kaiser
Markus
M
Huber
Robert
R
Schaller
Andreas
A
D002118:Calcium / Q000378:metabolism*; D020134:Catalytic Domain / Q000235:genetics; D003460:Crystallization; D004789:Enzyme Activation; D004795:Enzyme Stability; D018551:Solanum lycopersicum / Q000201:enzymology* / Q000235:genetics; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013381:Subtilisins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
D013381:Subtilisins; C119297:subtilase, plant; D002118:Calcium