BINDING OF ACRYLONITRILE TO PARVALBUMIN

A previous study has shown that acrylonitrile (ACN) has a long half-li fe in rainbow trout muscle and that [C-14]ACN appears to be bound to a 10,000-Da protein in muscle. The labeled protein was purified from mu scle of trout exposed to [C-14]ACN, separated on 20% SDS-PAGE, and dig ested for amino acid analysis and sequence analysis, These studies ind icated that the labeled protein was the Ca2+-binding protein parvalbum in. Parvalbumin is an important calcium-binding protein thought to be involved in the regulation of calcium levels in various parts of the b ody ranging from neurons to fast-twitch muscle contractions. To study the reaction between parvalbumin and [C-14]ACN, frog parvalbumin was i ncubated with [C-14]ACN in vitro under various conditions. These studi es indicated that the maximum labeling occurred at 1 nmol/nmol parvalb umin and at pH 7. Amino acid analysis of the labeled protein indicated that the labeled amino acid was probably histidine, and endoproteinas e Glu-C (V-8) digestion studies revealed that the C-14 was in the 1-81 amino acid segment of the protein, an area that contains two histidin es. (C) 1996 Society of Toxicology