1yu2
From Proteopedia
Major Tropism Determinant M1 Variant
Structural highlights
Function[Q775D6_BPBPP] Tail fiber protein located at the distal ends of the fibers that binds to the adhesion receptors on the host surface, thereby determining the host range. The phage can alter its tropism by modifying this protein. Variants are expressed through a diversity-generating retroelement (DGR) that creates mutant copies of a template repeat and replaces the end of the tail fiber receptor-binding protein with these sequences, thus changing the host range. Milliards of variants of the fiber receptor-binding protein can be created with this system.[1] Publication Abstract from PubMedOnly few instances are known of protein folds that tolerate massive sequence variation for the sake of binding diversity. The most extensively characterized is the immunoglobulin fold. We now add to this the C-type lectin (CLec) fold, as found in the major tropism determinant (Mtd), a retroelement-encoded receptor-binding protein of Bordetella bacteriophage. Variation in Mtd, with its approximately 10(13) possible sequences, enables phage adaptation to Bordetella spp. Mtd is an intertwined, pyramid-shaped trimer, with variable residues organized by its CLec fold into discrete receptor-binding sites. The CLec fold provides a highly static scaffold for combinatorial display of variable residues, probably reflecting a different evolutionary solution for balancing diversity against stability from that in the immunoglobulin fold. Mtd variants are biased toward the receptor pertactin, and there is evidence that the CLec fold is used broadly for sequence variation by related retroelements. The C-type lectin fold as an evolutionary solution for massive sequence variation.,McMahon SA, Miller JL, Lawton JA, Kerkow DE, Hodes A, Marti-Renom MA, Doulatov S, Narayanan E, Sali A, Miller JF, Ghosh P Nat Struct Mol Biol. 2005 Oct;12(10):886-92. Epub 2005 Sep 18. PMID:16170324[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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