**4. Conclusions**

The RSV G protein plays a vital role in attaching virion to the host cell membrane. This is the first report that describes the structural and conformational stability of the edG. In this paper, we reported the effect of pH on the structure of edG. We found that the edG was stable at physiological and highly acidic and alkaline conditions. However, a visible aggregation was observed at mild acidic pH values. The urea and GdmCl-induced denaturation studies of edG demonstrated that it follows a two-state transition mechanism. The fluorescence quenching, molecular docking, and MD simulation studies suggested strong binding between the edG and heparan sulfate. Our binding studies elucidate the involvement of heparan sulfate in host–pathogen interaction that is significant for viral infection. Finally, our data suggested that heparan sulfate mimicking compounds can be used to target the effective host–pathogen interaction.

**Author Contributions:** Experiment design and supervision, S.P., A.I. and A.H.; writing—original draft preparation, S.P., A.I. and A.H.; simulation and data analysis, M.A.I.; writing—review and editing, A.S., M.I.F., F.N.A., T.H., S.P., A.I. and A.A. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research work was supported by the grant funded by the Council of Scientific and Industrial Research, India [37(1697)17/EMR-II] and Central Council for Research in Unani Medicine, Ministry of Ayurveda, Yoga and Neuropathy, Unani, Siddha and homoeopathy (F.No.3-63/2019- CCRUM/Tech). The authors also extend their appreciation to the Deanship of Scientific Research at King Saud University for funding the work through the Research Group Project No. RG-1439-74.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Acknowledgments:** Abu Hamza acknowledges the Indian Council of Medical Research (VIR/ Fellowship/5/2018-ECD-I) and University Grant Commission, Government of India, for providing research fellowship. The authors also acknowledge the FIST program (SR/FST/LSI-541/2012) DST, India and Jamia Millia Islamia for providing equipment for research work.

**Conflicts of Interest:** The authors declare no conflict of interest.

**Sample Availability:** Samples of the recombinant plasmids with G protein gene are available from the authors.
