Try "homo sapiens"[organism] at NCBI site

Go to ncbi site http://www.ncbi.nih.gov, select protein and type "homo sapiens"[organism] in the search box. You should get 439813 hits.
From that page select "Display" to Fasta, and "Send to" to File. You should be able to down load all these sequences in Fasta format.
Repeat the above step to download sequences of other organisms.

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