ALUMINUM FLUORIDE INTERACTIONS WITH TROPONIN-C

The increasing interest in the metal ion aluminum fluoride and berylli um fluoride complexes as phosphate analogs in the myosin ATPase reacti on and in muscle fiber studies prompted the examination of their inter actions with the regulatory system of troponin and tropomyosin. In thi s work, the effects of these metal ion analogs on the spectral propert ies of the Ca2+-binding subunit of troponin, troponin C (TnC), were ex amined. In contrast to beryllium fluoride which did not change the spe ctral properties of TnC, aluminum fluoride binding induced an increase in both the alpha-helicity and the tyrosine fluoresence of TnC and ex posed a hydrophobic region on this protein for fluorescent probe bindi ng. Aluminum fluoride also reduced the Ca2+ and/or Mg2+-induced change s on TnC. These results indicate a direct interaction of aluminum fluo ride with TnC and merit consideration in designing muscle fiber experi ments with this phosphate analog.