Is it common for bridges to from between cysteines that are this close?
Not necessarily. In general, cysteines that are far apart in sequence can contribute more to the stability of a protein fold.
Since these two cysteines are so close in sequence, we can assume that this disulfide bond contributes very little to the stability of the protein. This makes sense, if we consider that this protein is involved in regulating the reduction potential of the cell: In order for the protein to function, the disulfide should be readily oxidized (formed) or reduced (broken) in response to changing conditions in the cell. This particular protein must remain folded even when the disulfide bond is reduced, so that the two cysteines are properly positioned and ready to bond.
I see! So, this is a redox potential buffer, analogous to a pH buffer! Thank you for the response!