nCoV_info

PRRA [nucleotides CTCCTCGGCGGG or TCCTCGGCGGGC, depending how you align ]
is the amino-acid-furin cleavage site ("FCS") inserted into SARS2 at the S1-S2 border in the spike protein.
It is not seen in the similar bat or pangolin viruses, so ir was speculated that it was
inserted in a lab , as done in similar experiments on IBV=infectious bronchitis virus,
 a coronavirus in birds, for which they are trying to create chicken-vaccines.

there are 2 such FCS in some coronaviruses :

CTCCTCGGCGGG = insertion
TCTCCTCGGCGGGCACGT , SARS2  , spike , 2038-2055
  S  P  R  R  A  R
AAACCAAGCAAGAGGTCATTTATTGAAGATCTACTTTTC , SARS2,spike,2431-2469
  K  P  S  K  R  S  F  I  E  D  L  L  F
AGTCCTAGAAGGCGTTCTTTTATTGAAGACCTTCTATTT , IBV  ,spike,2056-2094,AY761141
  S  P  R  R  R  S  F  I  E  D  L  L  F 

AGTCCTAGAAGGCG
 CTCCTCGGCGGG
 x----x-xx--x


https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5413309/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6832359/pdf/viruses-11-00972.pdf