The interaction of purified rabbit bone collagenase with purified rabbit bone metalloproteinase inhibitor.

1. Pure rabbit bone metalloproteinase inhibitor (TIMP) bound tightly to pure rabbit bone collagenase with an apparent Kd of 1.4 X 10(-10) M. 2. The molecular weight of the enzyme-inhibitor complex was found to be 54 000, but no enzyme activity could be recovered from the complex after treatment with either mercurials or proteinases. The complex thus differed from latent collagenase in terms of size, susceptibility to mercurials and behaviour on concanavalin A-Sepharose. 3. The interaction of the purified components was compared with that of crude collagenase and crude inhibitor in culture medium. Mercurial treatment partially reversed the inhibition in the crude system, but not when the purified components were used. 4. The significance of the results is discussed in relation to the extracellular control of the activity of collagenase.