For 10 points, name this element found in methionine and cysteine that gives rotting eggs their bad smell.
Hyaluronan is unique among GAGs in that it doesn't contain an ion with this element. Incorporation of this element into glycosaminoglycans is accomplished in the Golgi apparatus by PAPS. Active sites of molybdenum containing nitrogenases have FeMoco, whose structure includes cubes containing this non-metal. Rieske proteins contain clusters with two atoms of this element bound to two of iron. This element is replaced by (*) selenium in one amino acid. Phosphorus and this element were used as labels in the HersheyChase experiment. The start codon codes for an amino acid with this element in its side chain, and a type of bond named for this element has two thiol groups. For 10 points, name this element found in methionine and cysteine that gives rotting eggs their bad smell.
Hyaluronan is unique among GAGs in that it doesn't contain an ion with this element.
sulfur [prompt on "S"]