GC content
The GC content reflects the percentage of guanine and cytosine bases in the nucleotide sequence. The average GC content in Hsp60 sequences and genomes for 17 phyla was calculated using database 2 and 20808 reference genomes obtained from the NCBI Genome database (https://www.ncbi.nlm.nih.gov/genome/), respectively (Supplementary, GC-content and ENC).
The GC content of the first, second and third codon positions (GC1, GC2, and GC3, respectively) is required to evaluate their contribution to the GC content and is calculated by equation (3):
\(\text{GC}_{n}=\ \frac{G_{n}+\ C_{n}}{N}\) (3),
where n is the base position in the codon (n = 1, 2, 3);Gn and Cn are the number of guanine and cytosine bases in the n-position of the codons; Nis the number of codons in the sequence.