Structural stability study of two mucin SEA domains.

MARTÍN E. NOGUERA; MARÍA E. PRIMO; LAURA N.F. SOSA ; MARIO R. ERMÁCORA

Salta

Congreso; 3rd Latin American Protein Society Meeting.; 2010

SAD, CeBEM, Latin American Protein Society

Transmembrane mucins are large glycoproteins involved in diverse functions ranging from covering apical cell surfaces to intracellular cell signaling. Numerous studies have shown aberrant expression patterns of mucins MUC1 and MUC16 in human tumors and serum, and these proteins are serum markers widely used to monitor ovarian cancers. Most of the cell surface mucins have at least one SEA domain in the extracellular region. The global sequence identity of the SEA domain family is very low, and the exact function of this module is unknown. With the ultimate goal of understanding whether the few residues conserved in the sequences of this family are important for achieving the three-dimensional structure or necessary for function, we have begun a comparative study of the structural properties of the SEA domain of the mucins human MUC1 and the murine homologue of MUC16. The SEA domain were expressed in E. coli and purified from the soluble fraction. MUC1 SEA domain is found in a heterodimeric single domain form. To study the stability, both purified proteins were subjected to thermal unfolding. Although transitions are irreversible in the tested conditions, it was observed that the proteins are very stable against thermal denaturation. The stability of both proteins was characterized by isothermal denaturant unfolding. The conformational changes were monitored by following changes in circular dichroism. The analysis revealed that the proteins are stable and remain folded at high concentrations of denaturant.