title: Ser/Thr-rich repetitive motifs as targets for phosphoglycan modifications in Leishmania mexicana secreted acid phosphatase.
abstract: The insect stage of the protozoan parasite Leishmania mexicana secretes a phosphomonoesterase in the form of a filamentous complex. The polypeptide subunits of this polymer are modified by phosphoglycans and/or oligomannosyl residues linked to phosphoserine. Based on peptide sequence data of a predominant 100 kDa protein of the filamentous complex, two tandemly arranged, single copy genes, lmsap1 and lmsap2, were cloned and sequenced. lmsap1 predicts a protein with features characteristic of acid phosphatases and a remarkable serine- and threonine-rich region of 32 amino acids close to the C-terminus. In the otherwise identical lmsap2 product, this region is extended to 383 amino acids and is composed of short Ser/Thr-rich repeats. Deletion analysis demonstrates that lmsap1 encodes the major 100 kDa protein of the complex while a minor 200 kDa component is derived from the lmsap2 gene. Null mutants of either gene retain the ability to secrete acid phosphatase filaments, while a deletion of both genes results in Leishmania defective in enzyme formation. The Ser/Thr-rich domains are the targets for phosphoglycan modifications as shown by the expression of secreted fusion proteins composed of these C-terminal regions and the N-terminal domain of a lysosomal acid phosphatase.
authors.affiliation: Max-Planck-Institut für Biologie, Abteilung Membranbiochemie, Tübingen, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Wiese
authors.forename: T
authors.initials: T
authors.lastname: Ilg
authors.forename: F
authors.initials: F
authors.lastname: Lottspeich
authors.forename: P
authors.initials: P
authors.lastname: Overath
mesh_terms: D000135:Acid Phosphatase / Q000032:analysis / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002240:Carbohydrate Sequence; D003001:Cloning, Molecular; D016054:DNA, Protozoan / Q000032:analysis; D017125:Genes, Protozoan / Q000235:genetics*; D007894:Leishmania mexicana / Q000201:enzymology* / Q000235:genetics; D008247:Lysosomes / Q000201:enzymology; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000378:metabolism; D015800:Protozoan Proteins; D012333:RNA, Messenger / Q000032:analysis; D016053:RNA, Protozoan / Q000032:analysis; D011993:Recombinant Fusion Proteins / Q000032:analysis / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion / Q000502:physiology; D012694:Serine / Q000378:metabolism; D013912:Threonine / Q000378:metabolism
chemical_list: D016054:DNA, Protozoan; D009844:Oligosaccharides; D015800:Protozoan Proteins; D012333:RNA, Messenger; D016053:RNA, Protozoan; D011993:Recombinant Fusion Proteins; D013912:Threonine; D012694:Serine; D000135:Acid Phosphatase; C093136:Lmsap1 protein, Leishmania mexicana