87 Cryo-EM Reconstruction of A Phage Encoded Chaperonin

Wednesday, November 4, 2009: 10:40 AM
Kohlberg (Camino Real Hotel)
Sudheer K. Molugu , Department of Chemistry, The University of Texas at El Paso, El Paso, TX
Zacariah Hildenbrand , Department of Chemistry, The University of Texas at El Paso, El Paso, TX
Nadia Hererra , Department of Chemistry, The University of Texas at El Paso, El Paso, TX
Ricardo Bernal , Department of Chemistry, The University of Texas at El Paso, El Paso, TX

Chaperonins are a class of protein macro molecules that are essential to all living organisms because of their role in protein folding. Here, we present the three-dimensional structure of the first virus encoded chaperonin isolated from the phage EL. In contrast to the structures of other known chaperonins, the seven fold symmetric structure of the EL chaperonin is wide open in the ATP bound state and closed in the ADP bound state. The conformational rearrangement of the domains with ATP hydrolysis caused the two rings to separate at their inter ring connections and work independently. This accounted to twice the number of folding active chaperonins. ATP binding caused the two half rings stack back to back and form a dual ringed tetradecameric structure. The open structure of the EL chaperonin was solved to 7 resolution where the secondary structural elements were clearly seen at the equatorial ring region and in the inter domain interactions. The closed structure of the EL chaperonin is at 15 resolution and conforms the presence of the alpha helical arrangement in the equatorial ring region which is a unique feature of the EL chaperonin in both the open and closed states.