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Spectroscopic study of an HIV-1 capsid protein major homology region peptide analog
C B Clish1, D H Peyton, E Barklis
1Department of Chemistry, Portland State University, OR 97207-0751, USA.
Abstract:
The capsid (CA) domain of retroviral Gag proteins possesses one subdomain, the major homology region (MHR), which is conserved among nearly all avian and mammalian retroviruses. While it is known that the mutagenesis of residues in the MHR will impair virus infectivity, the precise structure and function of the MHR is not known. In order to obtain further information on the MHR, we have examined the structure of a synthetic peptide encompassing the MHR of human immunodeficiency virus type I (HIV-1) CA protein. Multiple sequence alignment and secondary structure prediction indicate that the peptide could form 50% alpha-helix and 10% beta-sheet. In addition, circular dichroism studies indicate that, in the presence of 50% trifluoroethanol (TFE), the peptide adopts an alpha-helical structure over half of its length. Further analysis by proton nuclear magnetic resonance spectroscopy suggests that the C-terminal portion of the MHR forms a helix in aqueous solution. Upon the addition of TFE, the position of the helix remains nearly constant, but the magnitude of the changes in H alpha chemical shifts of the residues indicate a more stable helix. These results suggest that a helical C-terminus of retroviral MHRs may be integral to the function of this region.
Insights
The major homology region (MHR) of human immunodeficiency virus type I (HIV-1) capsid protein is crucial for viral infectivity. Our study reveals a helical C-terminus within the MHR, suggesting its importance for retroviral function.
Area of Science:
- Virology
- Structural Biology
- Biochemistry
Background:
- The capsid (CA) domain of retroviral Gag proteins contains a conserved major homology region (MHR).
- The MHR is essential for virus infectivity, but its precise structure and function remain largely unknown.
- Understanding the MHR's structure is key to understanding retroviral replication.
Purpose of the Study:
- To investigate the structure of a synthetic peptide representing the MHR of the human immunodeficiency virus type I (HIV-1) CA protein.
- To elucidate the secondary structure and conformational dynamics of the MHR.
- To identify potential structural elements critical for MHR function.
Main Methods:
- Multiple sequence alignment and secondary structure prediction.
- Circular dichroism (CD) spectroscopy in aqueous solution and with trifluoroethanol (TFE).
- Proton nuclear magnetic resonance (NMR) spectroscopy.
Main Results:
- Secondary structure prediction suggested a potential for significant alpha-helical content.
- CD studies indicated alpha-helical structure formation in the presence of TFE.
- NMR analysis revealed a helical C-terminal portion of the MHR in aqueous solution, with enhanced stability upon TFE addition.
Conclusions:
- The C-terminal region of the retroviral MHR likely forms a stable alpha-helix.
- This helical structure may be integral to the MHR's function in retroviral replication.
- Further structural insights into the MHR could inform antiviral strategies.