Food for Health


Date of this Version


Document Type



Nucleic Acids Research , 2024, 52 , D419–D425


Open Access


Anti-prokary otic immune sy stem (APIS) proteins, typically encoded b y phages, prophages, and plasmids, inhibit prokaryotic immune systems (e.g. restriction modification, to xin-antito xin, CRISPR-Cas). A gro wing number of APIS genes ha v e been characterized and dispersed in the literature. Here w e de v eloped dbAPIS ( https:// dbAPIS ), as the first literature curated data repository for experimentally verified APIS genes and their associated protein f amilies. T he k e y features of dbAPIS include: (i) e xperimentally v erified APIS genes with their protein sequences, functional annotation, PDB or AlphaFold predicted str uct ures, genomic context, sequence and str uct ural homologs from different microbiome / virome databases; (ii) classification of APIS proteins into sequence-based families and construction of hidden Mark o v models (HMMs); (iii) user-friendly web interface for data browsing by the inhibited immune system types or by the hosts, and functions for searching and batch downloading of pre-computed data; (iv) Inclusion of all types of APIS proteins (e x cept f or anti-CRISPRs) that inhibit a v ariety of prokary otic defense systems (e.g. RM, TA, CB A SS , Thoeris, Gabija). The current release of dbAPIS contains 41 verified APIS proteins and ∼4400 sequence homologs of 92 families and 38 clans. dbAPIS will facilitate the discovery of novel anti-defense genes and genomic islands in phages, by providing a user-friendly data repository and a web resource for an easy homology search against known APIS proteins.