Inactivation of N-TIMP-1 by N-terminal acetylation when expressed in bacteria

The high‐affinity binding of tissue inhibitors of metalloproteinases (TIMPs) to matrix metalloproteinases (MMPs) is essential for regulation of the turnover of the extracellular matrix during development, wound healing, and progression of inflammatory diseases, such as cancer, atherosclerosis, and arthritis. Bacterially expressed N‐terminal inhibitory domains of TIMPs (N‐TIMPs) have been used extensively for biochemical and biophysical study of interactions with MMPs. Titration of N‐TIMP‐1 expressed in E. coli indicates, however, that only about 42% of the protein is active as an MMP inhibitor. The separation of inactive from fully active N‐TIMP‐1 has been achieved both by MMP affinity and by high‐resolution cation exchange chromatography at an appropriate pH, based on a slight difference of charge. Purification by cation exchange chromatography with a Mono S column enriches the active portion of N‐TIMP‐1 to >95%, with Ki of 1.5 nM for MMP‐12. Mass spectra reveal that the inactive form differs from active N‐TIMP‐1 in being N‐terminally acetylated, underscoring the importance of the free α‐NH2 of Cys1 for MMP inhibition. Nα‐acetylation of the CTCVPP sequence broadens the N‐terminal sequence motifs reported to be susceptible to α‐amino acetylation by E. coli N‐acetyl transferases. © 2008 Wiley Periodicals, Inc. Biopolymers 89: 960–968, 2008. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com