Ribosomal peptides and small proteins on the rise.

Genetically encoded and ribosomally synthesised small proteins and peptides act as important regulators in fundamental cellular processes, including gene expression, development, signalling and metabolism. Moreover, they also play a crucial role in the eukaryotic and prokaryotic defence against microorganisms and are extremely diverse in size and structure, and are often subject to extensive posttranslational modification. Recent technological advances now allow the analysis of the whole cellular transcriptome and proteome, revealing the presence of hundreds, long overlooked, alternative and short open reading frames (ORFs) in mRNA and supposedly non-coding RNAs. However, in many instances the biological roles of their translational products remain to be elucidated. Here we provide an overview on the intriguing structural and functional diversity of ribosomal synthesised peptides and newly discovered small proteins and peptides.