title: Expansion of Lysine-rich Repeats in Plasmodium Proteins Generates Novel Localization Sequences That Target the Periphery of the Host Erythrocyte.
abstract: Repetitive low complexity sequences, mostly assumed to have no function, are common in proteins that are exported by the malaria parasite into its host erythrocyte. We identify a group of exported proteins containing short lysine-rich tandemly repeated sequences that are sufficient to localize to the erythrocyte periphery, where key virulence-related modifications to the plasma membrane and the underlying cytoskeleton are known to occur. Efficiency of targeting is dependent on repeat number, indicating that novel targeting modules could evolve by expansion of short lysine-rich sequences. Indeed, analysis of fragments of GARP from different species shows that two novel targeting sequences have arisen via the process of repeat expansion in this protein. In the protein Hyp12, the targeting function of a lysine-rich sequence is masked by a neighboring repetitive acidic sequence, further highlighting the importance of repetitive low complexity sequences. We show that sequences capable of targeting the erythrocyte periphery are present in at least nine proteins from Plasmodium falciparum and one from Plasmodium knowlesi We find these sequences in proteins known to be involved in erythrocyte rigidification and cytoadhesion as well as in previously uncharacterized exported proteins. Together, these data suggest that expansion and contraction of lysine-rich repeats could generate targeting sequences de novo as well as modulate protein targeting efficiency and function in response to selective pressure.
authors: From the Institute of Structural and Molecular Biology, Department of Biological Sciences, Birkbeck and University College London, London WC1E 6BT, United Kingdom.
authors: Heledd M
authors: HM
authors: Davies
authors: From the Institute of Structural and Molecular Biology, Department of Biological Sciences, Birkbeck and University College London, London WC1E 6BT, United Kingdom.
authors: Konstantinos
authors: K
authors: Thalassinos
authors: From the Institute of Structural and Molecular Biology, Department of Biological Sciences, Birkbeck and University College London, London WC1E 6BT, United Kingdom a.osborne@ucl.ac.uk.
authors: Andrew R
authors: AR
authors: Osborne
mesh_terms: D000818:Animals; D004912:Erythrocytes / Q000378:metabolism / Q000469:parasitology*; D006801:Humans; D051379:Mice; D010963:Plasmodium falciparum / Q000235:genetics / Q000378:metabolism; D016790:Plasmodium knowlesi / Q000235:genetics / Q000378:metabolism; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism; D020449:Repetitive Sequences, Amino Acid
chemical_list: D015800:Protozoan Proteins
keywords: Plasmodium; cytoskeleton; host-pathogen interaction; intracellular trafficking; intrinsically disordered protein; low complexity sequences; malaria; protein evolution; protein targeting; tandem repeats