{Reference Type}: Journal Article {Title}: Exploring the Alternative Proteome with OpenProt and Mass Spectrometry. {Author}: Provencher N;Leblanc S;Jacques JF;Roucou X; {Journal}: Methods Mol Biol {Volume}: 2836 {Issue}: 0 {Year}: 2024 暂无{DOI}: 10.1007/978-1-0716-4007-4_1 {Abstract}: Proteogenomics has revealed the translation of unannotated open reading frames (ORFs) present in mRNAs and in noncoding RNAs (ncRNAs). OpenProt annotates all ORFs with a minimum of 30 codons in the transcriptome of several species and displays many functional features associated with the corresponding proteins. Two types of proteins are annotated: reference or canonical proteins which are proteins already annotated in UniProt, RefSeq, or Ensembl and noncanonical proteins. Noncanonical proteins form two groups: predicted novel isoforms that display a significant level of homology with a reference protein and alternative proteins that are new proteins with no significant homology to known proteins. This chapter describes how to check whether a gene and/or transcript contains multiple open reading frames and how to use OpenProt databases for the detection of alternative proteins and novel isoforms by mass spectrometry-based proteomics.