ProPr54 web server: predicting σ promoters and regulon with a hybrid convolutional and recurrent deep neural network.

σ serves as an unconventional sigma factor with a distinct mechanism of transcription initiation, which depends on the involvement of a transcription activator. This unique sigma factor σ is indispensable for orchestrating the transcription of genes crucial to nitrogen regulation, flagella biosynthesis, motility, chemotaxis and various other essential cellular processes. Currently, no comprehensive tools are available to determine σ promoters and regulon in bacterial genomes.