Whole Statue of Recognition by Enzyme Toward Substarates with Vague Signals

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(1) Structural information was obtained using fluorescence resonance energy transfer measurement (FRET). A series of the peptide substrate with different intervening lengths between the distal and proximal argines were synthesized and then covalently attached with the fluorescence acceptor and donnaor. When the substrates were bound to the enzyme, essentially the same distances between the probes were obtained. Such common length was also obtained when when FRET was conducted between the substrates and enzyme.(2) Among many precursor proteins some proteins lack the proximal arginine residue. Such precursors were still cleaved by mitochondrial processing peptidase (MPP). When the distal residue was changed to arginine, the processing efficiency was slightly elevated. This indicates that some interactions are still present between the S2-P2 positions.(3) MPP was shown to cleave the internal peptide bond of a fusion protein. Although the fusion protein had established the individual structure, MPP could attacked the peptide pond in a loosely structured domain.(4) The interaction between MPP and the substrates around regions other than the cleavage site was investigated using FRET measurement. The results indicated that a portion downstream from the cleavage site about 10 amino acids could emerge from the MPP pocket.