M.Murakami
and
T.Kouyama
(2016).
Crystal Structures of Two Isozymes of Citrate Synthase from Sulfolobus tokodaii Strain 7.
Biochem Res Int,
2016,
7560919.
PubMed id: 27656296
Crystal Structures of Two Isozymes of Citrate Synthase from Sulfolobus tokodaii Strain 7.
M.Murakami,
T.Kouyama.
ABSTRACT
Thermoacidophilic archaeon Sulfolobus tokodaii strain 7 has two citrate synthase
genes (ST1805-CS and ST0587-CS) in the genome with 45% sequence identity.
Because they exhibit similar optimal temperatures of catalytic activity and
thermal inactivation profiles, we performed structural comparisons between these
isozymes to elucidate adaptation mechanisms to high temperatures in thermophilic
CSs. The crystal structures of ST1805-CS and ST0587-CS were determined at
2.0 Å and 2.7 Å resolutions, respectively. Structural comparison reveals
that both of them are dimeric enzymes composed of two identical subunits, and
these dimeric structures are quite similar to those of citrate synthases from
archaea and eubacteria. ST0587-CS has, however, 55 ion pairs within whole dimer
structure, while having only 36 in ST1805-CS. Although the number and
distributions of ion pairs are distinct from each other, intersubunit ion pairs
between two domains of each isozyme are identical especially in interterminal
region. Because the location and number of ion pairs are in a trend with other
CSs from thermophilic microorganisms, the factors responsible for thermal
adaptation of ST-CS isozymes are characterized by ion pairs in interterminal
region.
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