The Egyptian report above, shows uridylate-specific endoribonuclease (NendoU). Gill-associated virus of shrimp (GAV) also has this NendoU, located in pp1ab. When we examine the precise amino acid sequences for NendoU of SARS-CoV-2 (positions 6453-6798) we note the differences in comparison to others:
SARS-CoV-2 sequence: SLENVAFNVVNKGHFDGQ
SARS-CoV sequence: SLENVAYNVVNKGHFDGQ
The only difference is the phenylalanine/tyrosine at position 7. Without mutating, position 501 of SARS-CoV spike is F (phenylalanine), though SARS-CoV-2 spike mutation at that position is N501Y, which is considered a major SARS-CoV-2 mutation.
So, Wuhan’s Zheng-Li Shi’s (2006) report for white spot syndrome of shrimp (WSSV) indeed links to a nidovirus of shrimp, of which the coronaviruses are members:
’Sequence alignments of the region downstream of the helicase indicate that the okavirus pp1ab also possesses 3’-to-5’ exonuclease, uridylate-specific endoribonuclease, and a C-terminal ribose-O-methyltransferase (2’-O-MT) motifs, which, in coronaviruses, have been shown to be essential to RNA synthesis and progeny virus production.’
(Cowley and Walker, Roniviruses, in Nidoviruses, ASM Press [2008])