BLAST search
BLAST (Basic Local Alignment Search Tool) can be used to compare nucleotide or protein sequence of interest to its sequence database and calculate the similarity between the sequences and matches. A BLAST result can help us identify proteins and domains that share similarity with the sequence of interest.
As we have chosen three human caspase 8 isoforms, one viral caspase 8, and two caspase 8 orthologues from model organisms, we decided to narrow down the database into only model organisms so that redundant results from the same species can be excluded and the extent of similarity in sequences across different species can be shown clearly. In addition, models (XM/XP) and uncultured / environmental sample sequence are excluded from the searches to ensure that there is no predicted structure listed in the result. We did not alter any other default settings.
BLAST search settings
Procaspase 8a isoform (Homo sapiens)
Using human caspase 8 isoform A as a standard for comparison, it is found that human caspase 9 and caspase 10, two other apoptosis initiator caspases, possess the greatest sequence similarity (≥90% identity) with human caspase 8, followed by Mus musculus orthologues (≥60% identity). On the other hand, orthologues in non-mammalian organisms, such as Danio rerio and Drosophila melanogaster, only demonstrate query cover of about 50% in which sequence similarity is only located on the catalytic domain near the N terminal. In this case sequence similarity between paralogues are greater than that between orthologues.
Procaspase 8l isoform (Homo sapiens)
Procaspase 8s isoform (Homo sapiens)
Caspase8p41 (Homo sapiens, cleaved by HIV)
Caspase 8 [Mus musculus]
dredd [Drosophila melanogaster]
