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Folding of an all beta-sheet protein, IL-1beta

James Covalt

Appointment Period: 1998-2001, Grant Years: [13,14,15,16]

James CovaltThe cytokine interleukin-1beta (IL-1beta) is involved in myriad physiological processes, including growth regulation and inflammation. IL-1beta is secreted from activated macrophages and monocytes and binds to the cell surface IL-receptor in order to elicit a particular biological response. However, it does not contain a classic leader sequence, and the translocation across the cell membrane occurs through a novel mechanism. Based on the available data, it was suggested that IL-1beta must be exported in a partially unfolded form and then fold to the biologically active conformation in the extra-cellular space.

My research focused on the area of protein folding and stability. I completed a mutational study on IL-1beta, which provided insight on the role that certain surface and core residues may play in the stability and folding of this protein. This work also showed that ordered water, which participate in main-chain hydrogen bonding between strands of the beta-structure of IL-1beta, may play an important role in stabilizing the native structure of this protein. My work also focused on the parameters that determine the mechanism of the folding for IL-1beta. This current work is using the construction of permutants of IL-1beta to get at this question. A permutant is a type of mutation in which the N and C termini of the WT protein are linked together with an amino acid linker region, and then new N and C termini are formed at other positions along the primary sequence. These are powerful investigative tools because they allow us to probe the importance of certain secondary structure elements in folding without changing the primary sequence of amino acids. Permutants also allow us to investigate the role that the topology of the native fold plays in determining the folding mechanism.

PUBLICATIONS (resulting from this training)

Covalt JC Jr, Roy M, Jennings PA. (2001) Core and surface mutations affect folding kinetics, stability and cooperativity in IL-1 beta: does alteration in buried water play a role? J Mol Biol. 307:657-69.

Covalt JC Jr, Cao TB, Magdaroag JR, Gross LA, Jennings PA. (2005) Temperature, media, and point of induction affect the N-terminal processing of interleukin-1beta. Protein Expr Purif. 41:45-52.