Table 1.

Effects of alkylating reagents on subunit combination

Reagent (concentration)	Combination
No Alkylating Agent	100%
4-vinylpyridine (0.1 M)	102.4%
3-(N-maleimidylpropionyl) biocytin (0.05 M)	105.1%
N-ethylmaleimide (0.05 M)	101.2%
iodoacetate (0.05 M)	69.2%
iodoacetate (0.6 M)	31.0%

Subunit combination was measured in the presence of the indicated alkylating agents. The concentrations of alkylating agents were far in excess of that of the subunits (0.1 mM). The only alkylating agent that reduced subunit combination was IA. As discussed, this effect was most likely due to the reaction of IA with noncysteine residues.