Coronavirus: What is D614G mutation? A strain that's ten times more infectious

New Delhi, Aug 17: After the emergence of SARS-CoV-2 in China in late 2019, and the rapid expansion of the COVID-19 pandemic in 2020, questions about viral evolution have come tumbling after. Will coronavirus be more infectious or transmissible?

However, recent studies have shown that D614G mutation in the spike protein of coronavirus makes it more infectious, transmissible, and deadly.

Recently, scientists in Malaysia detected a strain of the new coronavirus that's been found to be 10 times more infectious. The mutation called D614G was found in at least three of the 45 cases in a cluster that started when a restaurant owner and permanent resident returned to the country from India breaching his 14-day home quarantine.

According to Director General of Health Noor Hisham Abdullah's Facebook post, the D614G mutation was found by scientists in July 2020 and will probably lead to an existing vaccine study not to include or not effective in this mutation.

The D614G mutation has become the predominant variant in Europe and the U.S., with the World Health Organization saying there's no evidence the strain leads to a more severe disease.

What is D614G mutation?

A genetic mutation is characterized by a permanent change in the DNA sequence that may occur due to environmental factors (UV radiation), or due to an error during DNA replication process. Genetic mutations can be of many types, including missense, nonsense, insertion, deletion, duplication, frameshift, and repeat expansion mutations.

D614G mutation is a missense mutation wherein an alteration in single DNA base pair causes the substitution of aspartic acid (single-letter code: D) with glycine (single-letter code: G) in the protein encoded by the mutated gene.

The RNA codons that codes for aspartic acid and glycine are designed as GAU/GAC and GGU/GGC, respectively. Thus, a single mutation in the RNA codon causing A to G shift can lead to aspartic acid to glycine shift in the peptide sequence of the target protein.

Glycine is a nonpolar amino acid with a single hydrogen atom as its side chain; whereas, aspartic acid is a polar amino acid with an acidic side chain. Given the substantial difference between the basic nature of these amino acids, D614G mutation is expected to have significant biological implications.

Meanwhile, recent evidence suggests that viruses containing glycine residue at position 614 have now become the most prevalent variant globally.

Using suitable bioinformatic methods, scientists have found that G614G mutation in the viral spike protein is the most frequently occurring mutation across many geographical locations.

Moreover, scientists have shown that people infected with the G614 variant have higher viral RNA load in the upper respiratory tract than those infected with the D614 variant. However, D614G mutation is not associated with increased disease severity.

Because D614G mutation is located in the interface between neighboring spike protein protomers, it may modulate protomer-protomer interaction by disrupting between-protomer hydrogen bond formation.