Three-dimensional structure of thymidine phosphorylase from Escherichia coli at 2.8 A resolution.

The crystal structure of pyrimidine nucleoside phosphorylase in a closed conformation

“…The crystal structure of PYNP was determined with molecular replacement techniques using E. coli TP as a search model. PYNP has the same fold as that reported for E. coli TP [6], containing identical secondary structural features, with the exception of a three-stranded antiparallel β sheet in the α/β domain, which has not been reported previously. The strands of this new β sheet, labeled β1C-β3C, along with the previously reported secondary structural features (seventeen α helices, labeled H1-H17; a sixstranded mixed β sheet, labeled β1A-β6A; and a fourstranded antiparallel β sheet, labeled β1B-β4B) are shown in Figure 1a.…”

“…The active site of each subunit consists of a pyrimidinebinding site in the α domain and a phosphate-binding site across the cleft in the α/β domain. The distance between the phosphate-and pyrimidine-binding sites previously reported [6] is too large (e.g. 8-9 Å) for catalysis to occur unless the α and α/β domains move together.…”

“…Figure 7 shows the positions of the active-site residues around the substrates, as well as a schematic diagram of a proposed catalytic mechanism. Although several possible active-site residues have been identified from this structure, as well as the structures of E. coli TP [6,7], it should be emphasized that further studies, including kinetic analyses and site-directed mutagenesis, are necessary in order to positively identify and clarify the specific functions of residues involved in the catalytic mechanism.…”

“…Kinetic studies report that TP follows a sequential bi-bi mechanism where the order of substrate binding and product disassociation varies among species [2][3][4][5]. Detailed structural information of TP has so far come from the crystal structure of the Escherichia coli TP [6,7]. Each subunit of the TP dimer consists of a large mixed α-helical and β-sheet domain (α/β domain) separated from a smaller α-helical domain (α domain) by a large cleft.…”

Ανοσοϊστοχημική Μελέτη Της Αγγειογένεσης Στον Καρκίνο Της Ουροδόχου Κύστης

“…Περιγράφηκε από τους Friedkin και συνεργάτες το 1954 [212], ενώ απομονώθηκε στα μέσα του 1970 από την E. Coli και τη σαλμονέλα [214]. Στους προκαρυωτικούς οργανισμούς ονομάστηκε αρχικά ECGF και στους ευκαρυωτικούς TP με το μόριο να έχει μήκος 45 και 47 kDa αντίστοιχα [215,216], ενώ αρκετά αργότερα διαπιστώθηκε ότι τα δύο αυτά μόρια έκαναν την ίδια λειτουργία σε προκαρυωτικούς και ευκαρυωτικούς οργανισμούς με αποτέλεσμα να δοθεί ένα κοινό όνομα το PD-ECGF/TP ή απλώς TP. Να σημειώσουμε ότι ο όρος αιμοπεταλιακός ενδοθηλιακός αυξητικός παράγοντας δεν πρέπει να συγχέεται με τον αυξητικό παράγοντα των αιμοπεταλίων.…”