Cysteine-scanning analysis of the nucleobase-ascorbate transporter signature motif in YgfO permease of Escherichia coli: Gln-324 and Asn-325 are essential, and Ile-329-Val-339 form an alpha-helix.

The nucleobase-ascorbate transporter (NAT) signature motif is a conserved sequence motif of the ubiquitous NAT/NCS2 family implicated in defining the function and selectivity of purine translocation pathway in the major fungal homolog UapA. To analyze the role of NAT motif more systematically, we employed Cys-scanning mutagenesis of the Escherichia coli xanthine-specific homolog YgfO. Using a functional mutant devoid of Cys residues (C-less), each amino acid residue in sequence (315)GSIPITTFAQNNGVIQMTGVASRYVG(340) (motif underlined) was replaced individually with Cys.

Comparative substrate recognition by bacterial and fungal purine transporters of the NAT/NCS2 family.

We compared the interactions of purines and purine analogues with representative fungal and bacterial members of the widespread Nucleobase-Ascorbate Transporter (NAT) family. These are: UapA, a well-studied xanthine-uric acid transporter of A. nidulans, Xut1, a novel transporter from C.

Cloning and functional characterization of two bacterial members of the NAT/NCS2 family in Escherichia coli.

The coding potential of the genome of E. coli K-12 includes YgfO and YicE, two members of the evolutionarily conserved NAT/NCS2 transporter family that are highly homologous to each other (45% residue identity) and closely related to UapA of Aspergillus nidulans, a most extensively studied microbial member of this family. YgfO and yicE were cloned from the genome, over-expressed extrachromosomally and assayed for uptake of [(3)H]xanthine and other nucleobases, in E.

The recombinant subdomain IIIB of human serum albumin displays activity of gonadotrophin surge-attenuating factor.

Background: Gonadotrophin surge-attenuating factor (GnSAF) is an as yet unidentified ovarian factor that acts on the pituitary to attenuate the pre-ovulatory LH surge. In a previous study, GnSAF bioactivity was proposed to derive, at least in part, from a C-terminal domain (95peptide) of human serum albumin (HSA).

Methods And Results: We employ here the expression-secretion system of Pichia pastoris to produce and assay selected recombinant polypeptides of HSA for GnSAF activity.