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Figure 2.
Fig. 2. Structure-based sequence alignment of the P loop
and Lid regions. Lysine and arginine residues that make
phosphate interactions are underlined doubly and those that make
a stacking interaction with the adenine base are underlined
singly. TmpKs are unique in having a carboxylic acid situated at
the tip of the P loop (Glu-12 in TmpK[coli]). In type I TmpKs
(e.g., human and yeast), the following residue is an arginine
that has been shown to be catalytically important for the yeast
enzyme. Type II TmpKs (e.g., E. coli) lack this arginine, having
instead a number of basic residues in their Lid region: for
TmpK[coli], Arg-153 presumably fulfills a catalytically role
analogous to that of Arg-15 in yeast. Although the last Lid
arginine in TmpKs (Arg-158 in TmpK[coli]) aligns well with
catalytic arginines from pig adenylate kinase (AK[pig]) and
Dictyostelium uridylate kinase (UmpK[dicty]), it points away
from the active site, thus having no obvious catalytic role. The
eukaryotic TmpKs have no catalytic residues in the Lid region.
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