Pa. Osmulski et M. Gaczynska, A NEW LARGE PROTEOLYTIC COMPLEX DISTINCT FROM THE PROTEASOME IS PRESENT IN THE CYTOSOL OF FISSION YEAST, Current biology, 8(18), 1998, pp. 1023-1026
One eukaryotic proteolytic complex - the proteasome - is classed as th
e major nonlysosomal protease, by its known and suspected functions, i
ts size and its complexity [1,2], It seems improbable that other enzym
es may be capable of substituting, even partially, for the potent prot
easome, as this complex has a vital role in many cellular processes [1
-3], Nevertheless, it is possible to adapt cultured EL-4 mouse lymphom
a cells to survive in the presence of a specific inhibitor of the prot
easome [4], The inhibition of the proteasome in these adapted EL-4 cel
ls is accompanied by a dramatic increase in the activity of a new, as
yet uncharacterized, large proteolytic complex [4]. Here, we have pres
ented evidence that a similar proteolytic activity is constitutively p
resent in fission yeast, Schizosaccharomyces pombe, and that the yeast
and mouse enzymes share basic physicochemical properties. We have sho
wn that the S. pombe protease is found in two stable oligomeric forms,
both of which are peptidases, although only the larger form acts as a
proteinase. The relative amounts of the large and the small forms of
the protease in the complex depended on the growth phase of the yeast
culture and affected enzyme activity, suggesting that the activity of
the enzyme is regulated by its oligomerization status. We refer to the
new proteolytic complex as the 'multicorn' to indicate its analogy to
the archaebacterial tricorn protease [5].