Molecular and computational analysis of spike protein of newly emerged omicron variant in comparison to the delta variant of SARS-CoV-2 in Iraq

BACKGROUND: The Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV-2) has had a major impact on world health over the last 2 years. The emergence of SARS-CoV-2 variants, particularly concerning variants, may affect the virus’s pathogenicity, transmissibility, and vaccines potency. Both delta and the omicron variants have been designated by WHO as variants of concern. METHODS AND RESULTS: In this study, molecular techniques such as qPCR, conventional PCR, and sequencing were used to identify the first SARS-CoV-2 omicron variant that circulated in Iraq in January 2022. Bioinformatics and computational tools like phylogenetic analysis, predicted physical and chemical properties, stability, and molecular docking of the spike protein were used to compare the omicron with the delta variants. We found the receptor binding domain (RBD) and spike protein in omicron contain a greater number of hydrophobic amino acids compared to delta variant. We discovered a disorder–order conversion in RBD regions of the omicron variant, and this change may be important in terms of the effect of disordered residues/regions on spike protein stability and interaction with human angiotensin converting enzyme 2 (ACE2). Docking studies show that the omicron variant requires less energy to engage with ACE2, contributing to its higher binding affinity with human ACE2, consistent with more contagious transmission. CONCLUSION: This is the first molecular study of the circulated omicron and delta variants in Iraq, showing that the omicron variant in Iraq had a higher affinity for ACE2 than the delta variant, which may lead to higher transmissibility. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11033-022-07545-4.