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The role of the T‐loop of the signal transducing protein P II from Escherichia coli
Author(s) -
Jaggi Rene,
Ybarlucea Wendy,
Cheah Eong,
Carr Paul D.,
Edwards Karen J.,
Ollis David L.,
Vasudevan Subhash G.
Publication year - 1996
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(96)00737-5
Subject(s) - tyrosine , biology , phenylalanine , biochemistry , glutamine , serine , enzyme , site directed mutagenesis , mutagenesis , amino acid , mutation , gene , mutant
The 3D structure of P II , the central protein that controls the level of transcription and the enzymatic activity of glutamine synthetase in enteric bacteria revealed that residues 37–55 form the ‘T’ loop, part of which protrudes from the core of the protein. Within this loop are the only two tyrosine residues that occur in the polypeptide, and one of them, Tyr‐51, has been shown by chemical modification studies to be the site of uridylylation. Since tyrosine at position 46 is conserved in all known P II , proteins, oligonucleotide directed mutagenesis was used to investigate the role of the two residues. Changing Tyr‐51 to phenylalanine or serine abolished uridylylation. Altering tyrosine at position 46 to phenylalanine affected the rate of uridylylation of the protein. This latter mutation does not alter the structure of P II but the reduction in the uridylylation efficiency suggests a role for this residue in recognition and binding of the sensor enzyme uridylyl transferase.