Measurement of constitutive L-pyrrolidonyl peptidase activity from Streptococcus and Enterococcus using tetrazotized 0-dianisidine

The detection of L-pyrrolidonyl peptidase activity is extremely useful for the differentiation of Enterococcus species and Streptococcus pyogenes from other members of the family Streptococaceae. This analysis has generally been performed utilizing the hydrolyzable substrate L-pyrrolidonyl beta-naphthylamine. After the substrate was hydrolyzed, free beta-naphthylamine has been detected utilizing the reagent para-dimethylaminocinnamaldehyde. The cinnamaldehyde and naphthylamine reagents combine to form an orange color, much like the indole reaction. The use of the cinnamaldehyde reagent had several drawbacks however: color development was not sharp, and the reagent was difficult to produce, and it was not stable. A new indicator system employing tetrazotized 0-dianisidine was developed. An extremely deep burgundy colored complex resulted from the reaction between the new indicator and B-Naphthylamine. This diazo reagent showed excellent correlation with results obtained with para-dimethylaminocinnamaldehyde and yielded more objective, distinct endpoints. This inexpensive reagent can be utilized either in a liquid form or dired on paper discs.     

Correction to: Allocation in life cycle assessment of lignin

The International Journal of Life Cycle Assessment - The original version of this article unfortunately contained an inaccuracy.     

A new linear cyclin docking motif that mediates exclusively S‐phase CDK‐specific signaling

Cyclin‐dependent kinases (CDKs), the master regulators of cell division, are activated by different cyclins at different cell cycle stages. In addition to being activators of CDKs, cyclins recognize various linear motifs to target CDK activity to specific proteins. We uncovered a cyclin docking motif, NLxxxL, that contributes to phosphorylation‐dependent degradation of the CDK inhibitor Far1 at the G1/S stage in the yeast Saccharomyces cerevisiae. This motif is recognized exclusively by S‐phase CDK (S‐CDK) Clb5/6‐Cdc28 and is considerably more potent than the conventional RxL docking motif. The NLxxxL and RxL motifs were found to overlap in some target proteins, suggesting that cyclin docking motifs can evolve to switch from one to another for fine‐tuning of cell cycle events. Using time‐lapse fluorescence microscopy, we show how different docking connections temporally control phosphorylation‐driven target degradation. This also revealed a differential function of the phosphoadaptor protein Cks1, as Cks1 docking potentiated degron phosphorylation of RxL‐containing but not of NLxxxL‐containing substrates. The NLxxxL motif was found to govern S‐cyclin‐specificity in multiple yeast CDK targets including Fin1, Lif1, and Slx4, suggesting its wider importance.