Table 1 Stability of secondary structure formed by genome of coronavirus.

From: Human SARS-CoV-2 has evolved to reduce CG dinucleotide in its open reading frames

Genus

Virus

5′-UTR*

TSS-to-end

Virulence grade

Free energy (kcal/mol)

Stability index

Free energy (kcal/mol)

Stability index

Alphacoronavirus

Bat CoV CDPHE15

− 66.8

92 (H)

− 8,803.5

99 (H)

6

Bat CoV HKU10

− 61.3

84 (M)

− 8,029.1

90 (H)

5

Cat CoV1

− 68.8

95 (H)

− 7,963.0

89 (M)

5

Rat CoV

− 59.5

82 (M)

− 8,615.0

97 (H)

5

Mink CoV1

− 71.2

98 (H)

− 7,790.4

88 (M)

5

Bat CoV1

− 59.6

82 (M)

− 8,153.4

92 (H)

5

Bat CoV Sax2011

− 66.7

92 (H)

− 8,815.5

99 (H)

6

Bat CoV SC2013

− 57.3

79 (L)

− 8,712.4

98 (H)

4

PEDV

− 62.4

86 (M)

− 8,671.9

97 (H)

5

Bat CoV HKU2

− 64.3

88 (M)

− 8,313.0

93 (H)

5

Human CoV NL63

− 58.9

81 (M)

− 7,223.3

81 (M)

4

Human CoV 229E

− 55.6

76 (L)

− 7,982.5

90 (H)

4

Betacoronavirus

Human CoV HKU1

− 43.1

59 (L)

− 6,864.6

77 (L)

2

Human MERS-CoV

− 72.8

100 (H)

− 8,436.5

95 (H)

6

Human SARS-CoV

− 63.2

87 (M)

− 8,054.1

91 (H)

5

Human SARS-CoV-2

− 62.4

86 (M)

− 7,860.4

88 (M)

4

Bat CoV ZJ2013

− 58.9

81 (M)

− 8,328.2

94 (H)

5

Bat CoV HKU9

− 55.2

76 (L)

− 8,897.8

100 (H)

4

Deltacoronavirus

Wigeon CoV HKU20

− 51.8

71 (L)

− 8,273.2

93 (H)

4

Bulbul CoV HKU11

− 54.3

75 (L)

− 8,387.6

94 (H)

4

Heron CoV HKU19

− 54.9

75 (L)

− 7,687.2

86 (M)

3

Moorhen CoV HKU21

− 51.2

70 (L)

− 8,140.4

91 (H)

4

Gammacoronavirus

Whale CoV SW1

− 62.8

86 (M)

− 8,161.3

92 (H)

5

Turkey CoV

− 59.0

81 (M)

− 8,195.4

92 (H)

5

  1. *Fee energy of 5′-UTR (untranslated region) was obtained by using 200 nucleotides immediately upstream of TSS (translation start site) for secondary structure prediction. Free energy of TSS-to-end region is normalized using the average genome size (28,085 nt) of all surveyed coronaviruses based on actual accumulated free energy of a specific genome (Table S2). 5′-UTR region of human MERS-CoV and TSS-to-end region of bat CoV HKU9 have the lowest free energy respectively, which are thus given the highest stability index (100). H (high), M (medium) and L (low) indicate stability index of ≥ 90, 80 to 89, and < 79, respectively. Virulence grade is based on stability of both 5′-UTR and TSS-to-end regions, in which H, M and L stability is given 3, 2 and 1 points respectively. For example, human SARS-CoV has M and H stability in 5′-UTR and TSS-to-end regions. Thus, its virulence is of grade 5 (i.e. 2 + 3). Various grades of virulence are interpreted as follows: 6—very high, 5—high, 4—medium, 3—low and 2—very low. MERS: Middle East respiratory syndrome. SARS: severe acute respiratory syndrome. PEDV: Porcine epidemic diarrhea virus. The viruses listed in the table were selected to represent different subgenera of coronaviruses.