Oksana Sergeeva Research

Numerous proteins, including essential proteins such as tubulin and actin, are unable to fold to their native state in the cell without assistance from chaperones. Chaperonins are a family of chaperones that encapsulate their substrates and assist their folding in an ATP-dependent manner. Archaeal and eukaryotic cytosols contain Group II chaperonins, which have a double barrel structure and fold proteins inside a cavity in an ATP-dependent manner. The most complex of the chaperonins, the eukaryotic chaperonin, TCP-1 Ring Complex (TRiC), is a hetero-oligomeric complex composed of eight different Chaperonin Containing TCP-1 (CCT) subunits. Each CCT subunit may have distinct substrate recognition and ATP-binding properties. While aspects of the structure and function of the bovine and yeast TRiC have been characterized, studies of human TRiC have been limited.

We have isolated and purified endogenous human TRiC from HeLa suspensions cells and expressed each human CCT subunit individually in E. coli. The single CCT subunit approach gives us the opportunity to study the specificity and redundancy of each CCT subunit in a chaperonin context. Interestingly, purified CCT4 and CCT5 form two back-to-back rings consistent with that of the hetero-oligomeric TRiC. The human TRiC isolated from HeLa cells, and both CCT4 and CCT5 are active as assayed by the luciferase refolding assay and the human gammaD crystallin aggregation suppression assay. We are continuing to study the substrate recognition properties of human TRiC and the human CCT subunit homo-oligomers.

Poster Presentations/Abstracts:

Gordon Conference on Proteins 2011

Purification and Properties of Homo-Oligomeric Human CCT subunit by Oksana A. Sergeeva & Jonathan A. King. Presented at the 2012 FASEB Protein Folding in the Cell meeting.

Characterization of the substrate recognition and subunit assembly properties of homo-oligomeric human CCT subunits of TRiC by Sergeeva OA, Chen B, Haase-Pettingell C, Ludtke S, Chiu W & King JA. Presented at the 2013 Gordon Research Conference on Stress Proteins in Growth, Disease and Development.

Characterization of the substrate recognition and subunit assembly properties of homo-oligomeric human CCT subunits of TRiC Oksana A. Sergeeva, Cameron Haase-Pettingell and Jonathan A. King. Presented at the 2013 3rd USA_Mexico Workshop in Biological Chemistry: Protein Folding, Dynamics and Function.