Regulatory elements and functional implication for the formation of dimeric visinin‐like protein‐1

Size exclusion chromatographic analyses showed that Ca²⁺‐free VILIP‐1 contained both monomeric and dimeric forms, while no appreciable dimerization was noted with Ca²⁺‐free VILIP‐3. Swapping of EF‐hands 3 and 4 of VILIP‐1 with those of VILIP‐3 caused the inability of the resulting chimeric protein to form dimeric protein. Nonreducing SDS‐PAGE analyses revealed that most of the dimeric VILIP‐1 was noncovalently bound together. Reduced glutathione (GSH)/oxidized glutathione (GSSG) treatment notably enhanced the formation of disulfide‐linked VILIP‐1 dimer, while Ca²⁺ and Mg²⁺ enhanced disulfide dimerization of VILIP‐1 marginally in the presence of thiol compounds. Cys‐187 at the C‐terminus of VILIP‐1 contributed greatly to form S‐S‐crosslinked dimer as revealed by mutagenesis studies. The ability of GSH/GSSG‐treated VILIP‐1 to activate guanylyl cyclase B was reduced by substituting Cys‐187 with Ala. Together with disulfide dimer of VILIP‐1 detected in rat brain extracts, our data may imply the functional contribution of disulfide dimer to the interaction of VILIP‐1 with its physiological target(s). Copyright © 2008 European Peptide Society and John Wiley & Sons, Ltd.