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Microbes & Immunity Brachyspira pilosicoli novel outer membrane proteins

coli, function as both adhesins and invasins. Tia proteins Sequence-based annotation using PANNZER identified
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consist of eight TM β-sheets with four surface-exposed it as an OMBB protein. Sequence comparison across nine
loops and bind specific receptors on HCT8 human B. pilosicoli strains revealed 183 variations within the first
ileocecal epithelial cells. 152 seven strands of the β-barrel (Figure 4H and Table S5),
BP951000_RS08300 is predicted to contain a secretory indicating high variability across its 232-residue sequence.
signal peptide, and its AlphaFold 3 model revealed an 3.2.2.19. BP951000_RS01590
elliptical eight-stranded β-barrel, with two extended
β-strands projecting extracellularly (Figure 4F). Structural BP951000_RS01590, annotated as a hypothetical protein,
alignment showed the highest similarity to N. meningitidis is predicted to contain a secretory signal peptide. LipoP
NspA (PDB ID: 1P4T) (Tables 2 and S3). Foldseek analysis predicted a TMH at the N-terminal. The structural
identified structural homology with an OmpA family model revealed an eight-stranded β-barrel architecture
protein of Brachyspira hampsonii 30446, suggesting (Figure 4I) and additional short β-strands and α-helices
potential involvement in adhesion, invasion, intracellular extending extracellularly. As identified by DALI, structural
survival, or immune modulation. EggNOG mapper homology was highest with P. aeruginosa OprG (PDB ID:
further predicted lipid A 3-O-deacylase activity, which 2X27) (Tables 2 and S3), an OmpW family protein involved
modifies lipid A structure to facilitate immune evasion. in catabolism and uptake of hydrophobic molecules,
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Collectively, structure- and sequence-based evidence including hydrocarbons. Foldseek identified the closest
suggests that BP951000_RS08300 is a multifunctional structural match with an uncharacterized protein of
OMP, potentially involved in host interaction and immune B. pilosicoli P43/6/78. PANNZER analysis predicted the
modulation. Sequence comparison across nine B. pilosicoli protein to be a cell surface protein, suggesting a possible
strains revealed three variations (L143, N156, and S200) role in host–pathogen interaction. Sequence variation
(Figure 4F; Tables 3 and S4), all located in the β-barrel analysis across nine B. pilosicoli strains revealed three
domain (Table S4). variations (V205, I215, and V221), all located in the TM
β-barrel domain (Figure 4I, Tables 3 and S4).
3.2.2.17. BP951000_RS05490
3.2.2.20. BP951000_RS08295
BP951000_RS05490 is annotated as a hypothetical protein
in NCBI and as a Tia invasion determinant in UniProt. BP951000_RS08295, annotated as a Tia invasion
SignalP predicted a secretory signal peptide, whereas LipoP determinant, is predicted to carry a secretory signal
classified it as cytoplasmic. The AlphaFold 3 model revealed peptide. The AlphaFold 3 model revealed an eight-
an eight-stranded β-barrel architecture (Figure 4G). DALI stranded β-barrel with two elongated strands, forming an
analysis identified N. meningitidis NspA (PDB ID: 1P4T) elliptical pore on the extracellular side (Figure 4J). DALI
as the closest structural match (Tables 2 and S3). As a analysis identified the best structural alignment with N.
structural homolog of NspA, BP951000_RS05490 may play meningitidis NspA (PDB ID: 1P4T) (Tables 2 and S3),
similar roles in host interaction and immune modulation, suggesting potential roles in adhesion and immune
as discussed in Section 3.2.5. PANNZER annotation also evasion, similar to NspA (Section 3.2.5). Sequence-based
identified the protein as a Tia invasion determinant, annotation indicated adhesive function and potential
aligning with its UniProt classification. Comparative lipid A 3-O-deacylase activity, potentially contributing
sequence analysis across nine B. pilosicoli strains revealed to immune evasion. Among nine B. pilosicoli strains, six
61 variations distributed throughout the sequence and two variations were detected (N34, I49, V123, S141, I144, and
deletions (Figure 4G and Table S5). V167), with N34 located in the ECL region and the others
in the β-barrel domain (Figure 4J, Tables 3 and S4).
3.2.2.18. BP951000_RS07500
3.2.2.21. BP951000_RS08975
BP951000_RS07500, annotated as a hypothetical protein,
is predicted to contain a secretory signal peptide. The BP951000_RS08975 is annotated as a TonB-dependent
AlphaFold 3 model predicted an eight-stranded β-barrel receptor (TBDR) domain-containing protein in NCBI,
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structure (Figure 4H). Structural alignment identified and as a Ser/Threonine protein kinase in UniProt. TBDR
the closest match with the β-barrel domain of E. coli domain-containing proteins transport substrates across
K-12 OmpA (PDB ID: 9FZC) (Tables 2 and S3). Unlike the OM using the proton motive force, transmitted via
E. coli OmpA, BP951000_RS07500 lacks the periplasmic the TonB−ExbB−ExbD complex. 114,154 SignalP predicted
domain. Given that OmpA is involved in phage binding, a secretory signal peptide. AlphaFold 3 revealed a
vesicle transport, conjugation, and membrane integrity, 13-stranded incomplete β-barrel, likely forming a dimer or
BP951000_RS07500 may perform similar functions. 101-109 a higher-order oligomer (Figure 5A). Attempts to model a

Volume 2 Issue 4 (2025) 99 doi: 10.36922/MI025230050