Double homology domain

The crystal structure of the tandem Src-homology 2 (SH2) domain from Syk kinase in complex with a double phosphorylated ITAM peptide has been determined at a resolution of 3 A [13]. The two adjacent Syk C-terminal and N-terminal SH2 domains are required for localization to the membrane and are fundamentally important in the activation of Syk kinase. If the interaction of the... 

In the area of mononuclear nonheme iron enzymes, x-ray crystal structures are now also available for the catalytic domain of human phenylalanine hydroxylase [18] and naphthalene 1,2-dioxygenase [19]. The mononuclear iron site of phenylalanine hydroxylase resembles the 2-His-l-Asp site of tyrosine hydroxylase, a result anticipated by sequence homology. More interestingly, naphthalene 1,2-dioxygenase, which catalyzes the c/ s-dihydroxylation of arene double bonds in the biodegradation of aromatics, also has a Fe(His)2(Asp) iron site. These two enzymes augment the increasing number of mononuclear nonheme iron enzymes with a common Fe(His)2(carboxylate) facial triad motif [20],... 

SU (surface glycprotein) (gpl20) No homology to MuLV SU or other proteins. Inner /I-sandwich, bridging (3 sheet and double /I-barrel outer domain protease, antiparallel j3, like other aspartyl proteases integrase, N-terminal domain is helical, containing helix-turn-helix motif core domain, RNase H-like (mixed 0 with helices on either side)... 

Aravind L, Koonin EV. Prokaryotic homologs of the eukaryotic DNA-end-binding protein Ku, novel domains in the Ku protein and prediction of a prokaryotic double-strand break repair system. Genome Res. 2001 11 1365-1374. 

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