title: Hemoglobin receptor in Leishmania is a hexokinase located in the flagellar pocket.
abstract: Hb endocytosis in Leishmania is mediated through a 46-kDa protein located in the flagellar pocket. To understand the nature of the Hb receptor (HbR), we have purified the 46-kDa protein to homogeneity from Leishmania promastigote membrane. Purified HbR specifically binds Hb. The gene for HbR was cloned, and sequence analysis of the full-length HbR gene indicates the presence of hexokinase (HK) signature sequences, ATP-binding domain, and PTS-II motif. Four lines of evidence indicate that HbR in Leishmania is a hexokinase: 1) the recombinant HbR binds Hb, and the Hb-binding domain resides in the N terminus of the protein; 2) recombinant proteins and cell lysate prepared from HbR-overexpressing Leishmania promastigotes show enhanced HK activity in comparison with untransfected cells; 3) immunolocalization studies using antibodies against the N-terminal fragment (Ld-HbR-DeltaC) of Ld-HbR indicate that this protein is located in the flagellar pocket of Leishmania; and 4) binding and uptake of (125)I-Hb by Leishmania is significantly inhibited by anti-Ld-HbR-DeltaC antibody and Ld-HbR-DeltaC, respectively. Taken together, these results indicate that HK present in the flagellar pocket of Leishmania is involved in Hb endocytosis.
authors.affiliation: National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110067, India.
authors.forename: Ganga
authors.initials: G
authors.lastname: Krishnamurthy
authors.forename: Rajagopal
authors.initials: R
authors.lastname: Vikram
authors.forename: Sudha B
authors.initials: SB
authors.lastname: Singh
authors.forename: Nitin
authors.initials: N
authors.lastname: Patel
authors.forename: Shruti
authors.initials: S
authors.lastname: Agarwal
authors.forename: Gauranga
authors.initials: G
authors.lastname: Mukhopadhyay
authors.forename: Sandip K
authors.initials: SK
authors.lastname: Basu
authors.forename: Amitabha
authors.initials: A
authors.lastname: Mukhopadhyay
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D005407:Flagella / Q000502:physiology*; D006454:Hemoglobins / Q000378:metabolism*; D006593:Hexokinase / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D007893:Leishmania donovani / Q000201:enzymology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D006454:Hemoglobins; D015800:Protozoan Proteins; D011994:Recombinant Proteins; D000255:Adenosine Triphosphate; D006593:Hexokinase