MLPs are more numerous in comparison with DLPs
Out of the 5,569 pathogen proteins from 630 pathogens, a total of 5,255 proteins from 612 pathogens were involved in mimicry of the host interactor proteins using similar domains or motifs. The DLPs in the entire database were found to be 2,06,449 whereas the MLPs were found to 38,45,643. The number of DLPs and MLPs for each pathogen category are listed in Table 1. Viruses showed the highest number of DLPs and MLPs, likely to be due to the preponderance of virus HP-PPIs in the data.
Interestingly, of the total 61,215 HP-PPIs reported, only 1,549 were found to be characterized by domain mimicry whereas 49,266 were found to characterized by mimicked motifs. The total number of HP-PPIs, the fraction of HP-PPIs characterized by mimicked domains and by motifs were compared pathogen categories and are shown in Figure 3. Motif mimicry dominates in number over domain mimicry across the known HP-PPIs across all pathogen categories. Interestingly, as evident from Table 1, a large number of DLPs were also found in viruses (1,14,899), but were concentrated in only 822 HP-PPIs (or 1.7%) of the entire viral interactome as depicted in Figure 3. Conversely, in case of Fungi, very few HP-PPIs have been reported but still a large proportion of them were found to be characterized by mimicked candidates. Previous studies have reported the extensive use of motif mimicry by viral proteomes (25, 52-54). A reason for this monopoly can be that viruses being obligately intra cellular, incapable of synthesizing the DNA or RNA (25), and having a rapidly evolving genome need to hijack the major host processes which includes various metabolic and cellular signalling pathways. Our data indicates that molecular mimicry may be comparatively much more frequent in case of fungi. However, our results about frequency should be treated with caution as the mapping of the host pathogen interactome is far from complete.