Cytomegalovirus basic phosphoprotein (pUL32) binds to capsids in vitro through its amino one-third

Area of Science:

• Virology
• Molecular Biology
• Structural Biology

Background:

• The cytomegalovirus (CMV) basic phosphoprotein (BPP) is a tegument protein associated with the viral capsid.
• Understanding BPP-capsid interactions is crucial for elucidating CMV virion structure and infection mechanisms.

Purpose of the Study:

• To investigate the specific interaction between CMV BPP and viral capsids.
• To identify the region of BPP responsible for capsid binding.
• To determine if this interaction is conserved between different CMV species.

Main Methods:

• In vitro synthesis of radiolabeled simian CMV (SCMV) BPP.
• Incubation of labeled BPP with isolated SCMV capsids (B-capsids and C-capsids) or infected cell lysates.
• Analysis of binding using truncation mutants of SCMV BPP.
• Cross-species binding assays using human CMV (HCMV) BPP and SCMV capsids.

Main Results:

• SCMV BPP selectively binds to SCMV B-capsids and, to a lesser extent, C-capsids.
• The amino-terminal one-third of SCMV BPP mediates capsid binding.
• HCMV BPP (pUL32) also binds to SCMV capsids, and vice versa, indicating conserved binding sequences.
• Truncation analysis confirmed the amino-terminal one-third as the primary capsid-binding domain.

Conclusions:

• CMV BPP interacts specifically with the viral capsid through its amino-terminal region.
• The capsid-binding interface is conserved between SCMV and HCMV.
• This approach provides a framework for studying other protein-capsid interactions in CMV.