Identification of structural determinants for substrate binding and turnover by glucosyltransferase R supports the permutation hypothesis.
Segments that may crucially influence the catalytic behaviour of glucosyltransferases of the glucansucrase type were selected for modification. This was done by sequence alignments, followed by structural modelling of the putative catalytic domain, based on a permuted form of the glucosyltransferase R (GtfR) of Streptococcus oralis. Five selected regions, located in the C-terminal half of the potential catalytic domain, were replaced by segments found at equivalent positions in other glucosyltransferases. The exchanges of four of these regions significantly affected catalysis by GtfR. This identified C-terminal determinants for substrate binding and turnover and supports the so-called permutation hypothesis with respect to enzymes of the glucansucrase type. Based on the model, roles are proposed for specific residues. Major effects appear to involve a re-positioning of the C-terminal Tyr965 that very likely serves as a hydrophobic platform for the substrate.
Division of Microbiology, Helmholtz Centre for Infection Research, Braunschweig, Germany.
Anna Maria
AM
Swistowska
Sabine
S
Gronert
Sabine
S
Wittrock
Wera
W
Collisi
Hans-Jürgen
HJ
Hecht
Bernd
B
Hofer
D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D002384:Catalysis; D020134:Catalytic Domain / Q000502:physiology; D005964:Glucosyltransferases / Q000737:chemistry* / Q000235:genetics; D016695:Glycosyltransferases / Q000737:chemistry / Q000235:genetics; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D011485:Protein Binding / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology; D019533:Streptococcus oralis / Q000201:enzymology* / Q000235:genetics; D013379:Substrate Specificity / Q000502:physiology
D001426:Bacterial Proteins; D016695:Glycosyltransferases; D005964:Glucosyltransferases; C409029:GtfR protein, Streptococcus; C033837:alternansucrase