Dynamic state of the messenger RNA pool specific for extracellular protease in Bacillus amyloliquefaciens: Its relevance to the mechanism of enzyme secretion

Abstract

It has previously been shown that Bacillus amyloliquefaciens possesses a large pool of messenger RNA capable of supporting extracellular protease synthesis for over 60 minutes. The breakdown of this pool of mRNA has been followed by taking the amount of rifampicin-insensitive protease synthesis to be an indication of the level of the mRNA. In the presence of high levels of amino acids known to repress protease synthesis, the pool disappears more rapidly than in low levels of amino acids. Amino acids appear to affect neither the translation nor the stability of the mRNA since in the presence of rifampicin the pool disappears at approximately the same rate in high and low amino acids. It is concluded that transcription of the protease mRNA is repressed by amino acids and that the pool is the product of a dynamic equilibrium between synthesis and degradation. The degradation of protease mRNA is not obligatorily dependent on continued protein synthesis. It is speculated that the excessive production of mRNA may be a mechanism to ensure that sufficient intact mRNA reaches membrane localised translational sites to support extracellular enzyme synthesis despite its rapid degradation. In this sense it may represent a primitive prokaryote messenger transport system.