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Novel lineage‐specific transmembrane β‐barrel proteins in the endoplasmic reticulum of Entamoeba histolytica
Author(s) -
Santos Herbert J.,
Imai Kenichiro,
Makiuchi Takashi,
Tomii Kentaro,
Horton Paul,
Nozawa Akira,
Okada Kenta,
Tozawa Yuzuru,
Nozaki Tomoyoshi
Publication year - 2019
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/febs.14870
Subject(s) - endoplasmic reticulum , entamoeba histolytica , transmembrane protein , barrel (horology) , lineage (genetic) , biology , entamoeba , microbiology and biotechnology , stim1 , genetics , gene , geography , receptor , archaeology
β‐barrel outer membrane proteins ( BOMP s) are essential components of outer membranes of Gram‐negative bacteria and endosymbiotic organelles, usually involved in the transport of proteins and substrates across the membrane. Based on the analysis of our in silico BOMP predictor data for the Entamoeba histolytica genome, we detected a new transmembrane β‐barrel domain‐containing protein, EHI _192610. Sequence analysis revealed that this protein is unique to Entamoeba species, and it exclusively clusters with a homolog, EHI _099780, which is similarly lineage specific. Both proteins possess an N‐terminal signal peptide sequence as well as multiple repeats that contain dyad hydrophobic periodicities. Data from immunofluorescence assay of trophozoites expressing the respective candidates showed the absence of colocalization with mitosomal marker, and interestingly demonstrated partial colocalization with endoplasmic reticulum ( ER ) proteins instead. Integration to organellar membrane was supported by carbonate fractionation assay and immunoelectron microscopy. CD analysis of reconstituted proteoliposomes containing EHI _192610 showed a spectrum demonstrating a predominant β‐sheet structure, suggesting that this protein is β‐strand rich. Furthermore, the presence of repeat regions with predicted transmembrane β‐strand pairs in both EHI _192610 and EHI _099780, is consistent with the hypothesis that BOMP s originated from the amplification of ββ‐hairpin modules, suggesting that the two Entamoeba‐ specific proteins are novel β‐barrels, intriguingly localized partially to the ER membrane.