Release 8.3

Of mice and men: over 10'000 orthologous sequence pairs in UniProtKB/Swiss-Prot

Comparing orthologous proteins between mammalian species is very helpful to understand the biological basis underlying disease susceptibility or responsiveness to drugs, or simply to understand what makes us human and not simply another great ape.

Human protein sequences and those of all available mammalian orthologous sequences are annotated and compared in the frame of the UniProtKB/Swiss-Prot HPI annotation program (Human Proteomics Initiative). During the annotation process, sequence length, alternative splicing isoforms or even polymorphisms can be validated. In order to provide our users with a coherent view of mammalian proteomes, similar isoforms are shown for orthologous proteins from all mammalian species whenever possible.

The laboratory mouse is a widely used model organism and thus many murine sequences are available for annotation. It is currently the most highly represented non-human mammal with more than 11'000 entries, and 91% of these entries are orthologous to human proteins. Human-mouse orthologous pairs share 85% identity on average. About 36% of these pairs have identical sequence length and share 94% identity. The most highly conserved proteins are involved in core biological processes such as mRNA processing and transport, translation and ubiquitin-dependent protein degradation. In contrast, fast evolving proteins generally play roles in immunity, reproduction and signal transduction.

The percentage of identity between orthologous protein pairs in the most highly represented mammals in UniProtKB/Swiss-Prot is shown in the table below:

	             Orangutan   Bovine   Mouse     Rat
	Human            97.43    87.37   85.46   85.80
	Orangutan                 89.34   87.44   87.20
	Bovine                            83.99   84.80
	Mouse                                     93.48

UniProtKB/Swiss-Prot entries for orthologous proteins usually share the same protein mnemonic code in the entry name (ID line) and thus can be easily identified.