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J. Biol. Chem., Vol. 277, Issue 5, 3158-3167, February 1, 2002
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From the Methionine adenosyltransferase (MAT) catalyzes
the synthesis of s-adenosylmethionine (AdoMet), a metabolite that plays
an important role in a variety of cellular functions, such as
methylation, sulfuration, and polyamine synthesis. In this study,
genomic DNA from the protozoan parasite Leishmania infantum
was cloned and characterized. L. infantum MAT, unlike
mammalian MAT, is codified by two identical genes in a tandem
arrangement and is only weakly regulated by AdoMet. L. infantum MAT mRNA is expressed as a single transcript, with
the enzyme forming a homodimer with tripolyphosphatase in addition
to MAT activity. Expression of L. infantum MAT in Escherichia coli proves that the MAT and tripolyphosphatase
activities are functional in vivo. MAT shows sigmoidal
behavior and is weakly inhibited by AdoMet, whereas tripolyphosphatase
activity has sigmoidal behavior and is strongly activated by
AdoMet. Plasmids containing the regions flanking MAT2 were
fused immediately upstream and downstream of the luciferase-coding
region and transfected into L. infantum. Subsequent
examination of luciferase activity showed that homologous expression in
L. infantum promastigotes was dramatically dependent on the
presence of polypyrimidine tracts and a spliced leader junction site
upstream of the luciferase gene, whereas downstream sequences appeared
to have no bearing on expression.
Departamento de Farmacología y
Toxicología, Facultad de Veterinaria, Universidad de León
Campus de Vegazana s/n, 24071 León, Spain and the
¶ Dpto. de Biotecnología, Ciencias Biológicas y de
la Salud Universidad Autonóma Metropolitana-Iztapalapa
Avda. de Michoacán y la Purísima, s/n
Colonia Vicentina, Iztapalapa 09340, México D.F.
The nucleotide sequence(s) reported in this paper has been submitted to the GenBankTM/EBI Data Bank with accession number(s) AF031902.
§ To whom correspondence may be addressed: Dpt. Farmacología y Toxicología, Facultad de Veterinaria, Universidad de León, Campus de Vegazana s/n 24071 León, Spain. Tel.: 34-987-291-590; Fax: 34-987-291-252; E-mail: dftrrt@isidoro.unileon.es.This article has been cited by other articles:
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