4BV4:
reference: Cytokine Spatzle binds to the Drosophila immunoreceptor Toll with a neurotrophin-like specificity and couples receptor activation., Lewis M, Arnot CJ, Beeston H, McCoy A, Ashcroft AE, Gay NJ, Gangloff M, Proc Natl Acad Sci U S A. 2013 Nov 26. PMID: 24282309

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