THE N-TERMINUS OF THE MOLECULAR CHAPERONIN GROEL IS A CRUCIAL STRUCTURAL ELEMENT FOR ITS ASSEMBLY

The Escherichia coli heat-shock protein GroEL is a member of the highl y conserved family of tetradecameric chaperonins 60, which assist in t he folding and assembly of other proteins. Using site-directed mutagen esis, it is shown that replacement of the absolutely conserved amino a cid residue Lys-3 by arginine or isoleucine destabilizes the GroEL par ticle and that the replacement Lys-3 --> Glu completely blocks its for mation. The rank order of effects of these mutations on the stability of the GroEL particle correlates with the associated changes in net ch arge at that position. Our results show that the N terminus of GroEL i s a crucial structural element for its assembly.