A hypothesis explaining why so many pathogen virulence proteins are moonlighting proteins.

Area of Science:

• Biochemistry
• Immunology
• Molecular Biology

Background:

• Moonlighting proteins possess multiple functions within a single polypeptide chain.
• These proteins are frequently associated with essential ancestral functions and primary metabolism.
• A significant portion of known moonlighting proteins are implicated in pathogen virulence.

Purpose of the Study:

• To investigate why virulence proteins from pathogens often derive from ancestral biological functions, particularly primary metabolism.
• To explore the implications of conserved protein functions between pathogens and hosts on immune responses.
• To understand the potential link between epitope mimicry of conserved moonlighting proteins and autoimmune diseases.

Main Methods:

• Compilation of 698 moonlighting proteins in the MultitaskProtDB-II database.
• Analysis of the functional origins of virulence-associated moonlighting proteins.
• Hypothesis-driven investigation into protein conservation and immune evasion strategies.

Main Results:

• Approximately 25% of proteins in the MultitaskProtDB-II database exhibit moonlighting functions related to pathogen virulence.
• A hypothesis is proposed that high conservation between pathogen and host counterparts of these proteins contributes to immune evasion.
• Epitope mimicry between pathogen and host proteins is suggested as a potential cause of autoimmune diseases.

Conclusions:

• The conservation of ancestral functions, especially in primary metabolism, by pathogen virulence proteins is a key factor in their moonlighting roles.
• High sequence and functional conservation with host proteins may prevent the host immune system from mounting effective antibody responses against these pathogen proteins.
• This phenomenon of epitope mimicry could explain the limited success of vaccines targeting conserved moonlighting proteins and potentially contribute to autoimmune disorders.