= D. R. Davies
{c}
D. R. Davies is the published author name credited on a structural study of <Tn5 transposase>. The original 2000 paper lists a University of Wisconsin biochemistry affiliation. Its initials are retained here because the scientific byline establishes this contribution without establishing a full personal identity.<Three-dimensional structure of the Tn5 synaptic complex transposition intermediate by D. R. Davies and others>[Published byline, affiliation and Abstract; Science 289, 77–85]{ref}
Davies and collaborators determined a <protein>–<DNA> assembly at $2.3$ <ångströms> <crystallographic resolution>. The <protein dimer> held two <DNA> ends, with each end contacted by both subunits. The arrangement explained how one subunit could bind an end while the other supplied the <active site> for cleavage. It supplied a structural framework for understanding coordinated <DNA transposition>.<Three-dimensional structure of the Tn5 synaptic complex transposition intermediate by D. R. Davies and others>[Abstract: dimeric complex, shared DNA contacts and cleavage in trans]{ref}
The geometry is more revealing than a count of components. Imagine two subunits A and B and two <DNA> ends L and R. Knowing merely that the assembly contains two subunits and two ends leaves open an arrangement in which A independently processes L and B independently processes R. Contacts that span the two subunits instead couple recognition of an end to the partner's catalytic machinery. Such an arrangement provides a concrete reason why an isolated, correctly bound <DNA> end need not behave like the complete <transpososome>.
The quoted distance is $0.23$ <nanometres>, since one <ångström> is $0.1$ <nanometres>. <Crystallographic resolution> describes the spatial detail supported by the diffraction data; it is not a frame interval in a movie and does not mean that every atomic coordinate has an uncertainty of precisely $0.23$ <nanometres>. A static structure constrains possible <reaction mechanisms>, while the sequence and rates of chemical steps require additional evidence. The distinction matters whenever an attractive structural model is used to explain a dynamic <enzyme> reaction.
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