Very little is known about {HEAD ~ the roles} of {TAIL ~ four other SIR2 family members} found in yeast , nor about the function of homologs from other species 
of
Very little is known about { HEAD ~ the roles } of { TAIL ~ four other SIR2 family members } found in yeast , nor about the function of homologs from other species
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH