The process may be accelerated by the protein itself. "The prolific use of green fluorescent protein and its variants throughout cellular biology relies on the post-translational formation of the chromophore, which proceeds without the need for any additional enzymes or cofactors, except molecular oxygen."
Chem Soc Rev. 2009 Oct;38(10):2865-75. doi: 10.1039/b903641p. Epub 2009 Aug 26.
Green fluorescent protein: structure, folding and chromophore maturation.
Curr Opin Struct Biol. 2006 Dec;16(6):714-21. Epub 2006 Oct 24.
Fluorescent proteins: maturation, photochemistry and photophysics.