S.Zamora-Caballero
et al.
(2015).
Quaternary structure of Dioclea grandiflora lectin assessed by equilibrium sedimentation and crystallographic analysis of recombinant mutants.
Febs Lett,
589,
2290-2296.
PubMed id: 26226421
DOI: 10.1016/j.febslet.2015.07.020
The structural basis of the pH dependency of the dimer-tetramer transition
exhibited by Brinda's type II Diocleinae lectins was investigated by equilibrium
sedimentation and X-ray crystal structure determination of recombinant wild-type
and site-directed single and double mutants of the pH-stable tetrameric Dioclea
grandiflora lectin (r-αDGL). Releasing the peripheral site interdimeric contact
between R60 and D78 rendered a mutant displaying dimer-tetramer equilibrium in
the pH range equivalent to pKa±1 of the γ-COOH. Mutation of both histidines 51
and 131, but not the mutation of each His separately, abolished the formation of
the Diocleinae canonical tetramer in the pH range 2.5-8.5. The X-ray structure
of the double mutant r-αDGL H51G/H131N suggests that H131 plays a crucial role
in networking loop 114-125 residues from all four subunits at the central cavity
of the tetrameric lectin, and that H51 maintains the central cavity loops in a
proper spatial orientation to make H131-mediated interdimer contacts.
Links
