Fig. 1. Sir2p is part of a large stable multi-protein complex in yeast. (A) Elution profile of Sir2p fractionated on a gel-filtration column. A whole cell extract from ROY 1515 was fractionated on a Superose 6B gel-filtration column and 15 µl aliquots of each fraction were analyzed by protein immunoblotting using antisera specific to yeast Sir2p. (B) Partially purified fractions containing Sir2p were treated with either DNase I, RNase A or 500 mM KCl and then fractionated on a Superose 6B gel-filtration column followed by protein immunoblotting using antisera specific to yeast Sir2p.