title: The evolution and putative function of phosducin-like proteins in the malaria parasite Plasmodium.
abstract: Ubiquitous to the proteomes of all living species is the presence of proteins containing the thioredoxin (Trx)-domain. The best characterized Trx-domain containing proteins include the enzymes involved in cellular redox metabolism facilitated by their cysteine-containing active site. But not all members of the Trx-fold superfamily exhibit this catalytic motif, e.g., the phosducin-like (PhLP) family of proteins. Genome sequencing efforts have uncovered new Trx-domain containing proteins, and their redox activity and cellular functions have yet to be determined. The genome of the malaria parasite Plasmodium contains multiple thioredoxins and thioredoxin-like proteins which are of considerable interest given their role in the parasite's antioxidant defense. While adaptations within the Trx-domain have been studied, primarily with respect to redox active structures, PhLP proteins have not been examined. Using the uncharacterized phosducin-like protein from Plasmodium berghei PhLP-1, we investigated the evolution of PhLP proteins across all branches of the tree of life. As a result of our analysis, we have discovered the presence of two additional PhLP proteins in Plasmodium, PhLP-2 and PhLP-3. Sequence homology with annotated PhLP proteins in other species confirms that the Plasmodium PhLP-2 and PhLP-3 belong to the PhLP family of proteins. Furthermore, as a result of our analysis we hypothesize that the PhLP-2 thioredoxin was lost over time given its absence from higher-order eukaryotes. Probing deeper into the putative function of these proteins, inspection of the active sites indicate that PbPhLP-1 and PbPhLP-2 may be redox active while PbPhLP-3 is very likely not. The results of this phylogenetic study provide insight into the emergence of this family of Trx-domain containing proteins.
authors.affiliation: Department of Biology, Loyola University Chicago, 1032 W Sheridan Rd, Chicago, IL 60660, USA. cputonti@luc.edu
authors.forename: Catherine
authors.initials: C
authors.lastname: Putonti
authors.forename: Bryan
authors.initials: B
authors.lastname: Quach
authors.forename: Rachel L
authors.initials: RL
authors.lastname: Kooistra
authors.forename: Stefan M
authors.initials: SM
authors.lastname: Kanzok
mesh_terms: D000595:Amino Acid Sequence; D019143:Evolution, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D010961:Plasmodium / Q000145:classification / Q000235:genetics* / Q000378:metabolism*; D010962:Plasmodium berghei / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D013879:Thioredoxins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*
chemical_list: D013879:Thioredoxins