Recombinant Protochlamydia amoebophila UPF0758 protein pc1765 (pc1765)

Overview

Protochlamydia amoebophila is a bacterium belonging to the Parachlamydiaceae family, closely related to Chlamydiaceae, which includes major human pathogens . Unlike its pathogenic relatives, P. amoebophila exists as an obligate intracellular symbiont within free-living amoebae, specifically Acanthamoeba species . Proteomic analysis of Protochlamydia amoebophila has identified a comprehensive set of proteins involved in translation and energy generation within its elementary bodies . The protein pc1765, also known as Recombinant Protochlamydia amoebophila UPF0758 protein pc1765, is one such protein identified in P. amoebophila .

Characteristics of Protochlamydia amoebophila

Protochlamydia amoebophila exhibits several unique characteristics:

• It resides within a host-derived vesicular compartment called an inclusion .

• It modifies the inclusion membrane by inserting unique proteins to interact with and manipulate the host cell .

• The genome of P. amoebophila encodes several paralogous carrier proteins that belong to the nucleotide transporter (NTT) family .

• P. amoebophila lacks key genes for NAD+ biosynthesis, rendering it unable to synthesize NAD+ de novo .

Identification and Expression of pc1765

Proteomic studies have successfully identified the pc1765 protein in P. amoebophila . These studies involved:

• 2-D Reference Proteome Mapping: Establishing a detailed proteome map of the infectious stage of symbiotic chlamydia .

• Shotgun Proteomics: Complementing the 2-D analysis to enhance protein identification .

• Functional categories: Identifying proteins spanning a wide range of functional categories, from typical house-keeping proteins to putative virulence-associated proteins .

Furthermore, the expression of pc1765, classified as a hypothetical or unknown protein, has been demonstrated, indicating its active role within the bacterium .

Functional Insights from Proteomic Analysis

Proteomic analysis has provided insights into the functional roles of proteins like pc1765:

• House-keeping proteins: Identification of proteins necessary for basic cellular functions .

• Virulence-associated proteins: Discovery of proteins that may play a role in host-microbe interactions .

• Hypothetical proteins: Expression of proteins with unknown functions, suggesting novel biological mechanisms .

These findings highlight the ability of P. amoebophila to utilize its genetic repertoire, showcasing that its elementary bodies are well-equipped with proteins for transcription, translation, and energy generation .

Nucleotide Transporters (NTTs) in P. amoebophila

P. amoebophila possesses five paralogous carrier proteins belonging to the nucleotide transporter (NTT) family . Functional analysis of three P. amoebophila NTT isoforms—PamNTT2, PamNTT3, and PamNTT5—revealed their ability to transport nucleotides with unique substrate specificities and transport modes . PamNTT2 functions as a counter-exchange transporter with submillimolar affinities for all four RNA nucleotides, PamNTT3 catalyzes a unidirectional proton-coupled transport specific to UTP, and PamNTT5 mediates a proton-energized GTP and ATP import . The transcription of all NTT genes during intracellular multiplication highlights the bacterium's intimate connection with the host cell's metabolism .

Inclusion Membrane Proteins

P. amoebophila utilizes inclusion membrane proteins to interact with host cells . Genome-wide screening has identified 23 putative inclusion membrane proteins, and four of these (IncA, IncQ, IncR, and IncS) have been localized to the inclusion membrane . This conserved strategy for host cell interaction is shared among chlamydial symbionts and pathogens .