Further, they found that both long and short forms were essential for normal growth and that the short form was particularly important for DNA damage tolerance, suggesting that these fragments are not accidental but are made in a programmed manner.
Vass and Chien's new work shows that in some bacteria, short forms of DnaX are made instead by another method, proteolysis, with dramatic consequences for the cell, the biochemist says. "This type of convergent evolution results in similar protein outcomes, that is the generation of two forms through radically different mechanisms. This suggests that both long and short forms are crucial for all bacteria," he adds.
Protein degradation by energy-dependent proteases normally results in the complete destruction of target proteins, Chien notes. However, under particularly harsh artificial conditions in the test tube, these proteases can stall on certain targets. But until the recent UMass Amherst experiments, such an effect had never been seen inside a living bacterial cell, he adds.
Chien feels this mode of partial digestion could be useful in other bacteria to generate new functions from existing proteins and increasing the ability of a single gene to encode for multiple protein functions. This work was supported by NIH's National Institute for General Medical Sciences and by UMass Amherst.
|Contact: Janet Lathrop|
University of Massachusetts at Amherst