title: Structure-function relationships in the stereospecific and manganese-dependent 3,4-dihydroxyphenylalanine/tyrosine-sulfating activity of human monoamine-form phenol sulfotransferase, SULT1A3.
abstract: The human monoamine-form phenol sulfotransferase (PST), SULT1A3, has a unique 3,4-dihydroxyphenylalanine (Dopa)/tyrosine-sulfating activity that is stereospecific for their d-form enantiomers and can be stimulated dramatically by Mn(2+). This activity is not present in the simple phenol-form PST, SULT1A1, which is otherwise >93% identical to SULT1A3 in amino acid sequence. The majority of the differences between these two proteins reside in two variable regions of their sequences. Through the characterization of chimeric PSTs where these two regions were exchanged between them, it was demonstrated that variable Region II of SULT1A3 is required for the stereospecificity of its Dopa/tyrosine-sulfating activity, whereas variable Region I of SULT1A3 is required for the stimulation by Mn(2+) of this activity. Further studies using point-mutated SULT1A3s mutated at amino acid residues in these two regions and deletional mutants missing residues 84-86 and 84-90 implicate residue Glu-146 (in variable Region II of SULT1A3), as well as the presence of residues 84-90 of variable Region I, in the stereospecificity in the absence of Mn(2+). Residue Asp-86 (in variable Region I of SULT1A3), on the other hand, is critical in the Mn(2+) stimulation of the Dopa/tyrosine-sulfating activity of SULT1A3. A model is proposed, with reference to the reported x-ray crystal structure of SULT1A3, to explain how the normal role of SULT1A3 in dopamine regulation may be subverted in the presence of Mn(2+). These studies could be relevant in understanding the stereoselective action of SULT1A3 on chiral drugs.
authors.affiliation: Biomedical Research Center, The University of Texas Health Center, Tyler, Texas 75708, USA.
authors.forename: T Govind
authors.initials: TG
authors.lastname: Pai
authors.forename: Ila
authors.initials: I
authors.lastname: Oxendine
authors.forename: Takuya
authors.initials: T
authors.lastname: Sugahara
authors.forename: Masahito
authors.initials: M
authors.lastname: Suiko
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Sakakibara
authors.forename: Ming-Cheh
authors.initials: MC
authors.lastname: Liu
mesh_terms: D000595:Amino Acid Sequence; D015239:Arylsulfotransferase; D001483:Base Sequence; D018360:Crystallography, X-Ray; D017931:DNA Primers; D004295:Dihydroxyphenylalanine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008345:Manganese / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D015238:Sulfotransferases / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D014443:Tyrosine; D008345:Manganese; D004295:Dihydroxyphenylalanine; D015238:Sulfotransferases; D015239:Arylsulfotransferase; C403170:monoamine-sulfating phenol sulfotransferase