The amino acid sequence specificity of a protease from spores of Bacillus megaterium.

Previous work has shown that the degradation of 20% of total protein which occurs early in germination of Bacillus megaterium spores is initiated by an endoprotease. This enzyme is found only in the spore and is active only on the spore proteins degraded during germination. Action of the spore protease in vitro on the three major proteins (Proteins A, B, and C) which are degraded in vivo during germination results in cleavage of one (A and C protein) or two (B protein) peptide bonds. The sequences surrounding the cleavage sites are -Tyr-Glu- Ile-Ala-Ser-Glu-Phe- in the A protein, -Phe-Glu- Ile-Ala-Ser-Glu-Phe- in the C protein, and -Thr-Glu- Phe-Gly-Ser-Glu-Thr-, and -Thr-Glu- Phe-Ala-Ser-Glu-Thr- in the B protein, with cleavage taking place at the glutamyl bond noted by the arrow. The similarity of these four sequences suggests the possibility that the specificity of the spore protease may be due to its requirement for a specific pentapeptide sequence of the type -R-Glu-(Phe or Ile)-(Gly or Ala)-Ser-Glu-R- for recognition and cleavage. However, it is also possible that it is the conformation of the A, B, and C proteins which determines their site of cleavage by the spore protease.