1mss
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LARGE SCALE STRUCTURAL REARRANGEMENTS OF THE FRONT LOOPS IN MONOMERISED TRIOSEPHOSPHATE ISOMERASE, AS DEDUCED FROM THE COMPARISON OF THE STRUCTURAL PROPERTIES OF MONOTIM AND ITS POINT MUTATION VARIANT MONOSS
OverviewOverview
BACKGROUND: Wild-type triosephosphate isomerase (TIM) is a very stable, dimeric enzyme. This dimer can be converted into a stable monomeric, protein (monoTIM) by replacing the 15-residue interface loop (loop-3) by a, shorter, 8-residue, loop. The crystal structure of monoTIM shows that two, active-site loops (loop-1 and loop-4), which are at the dimer interface in, wild-type TIM, have acquired rather different structural properties., Nevertheless, monoTIM has residual catalytic activity. RESULTS: Three new, structures of variants of monoTIM are presented, a double-point mutant, crystallized in the presence and absence of bound inhibitor, and a, single-point mutant in the presence of a different inhibitor. These new, structures show large structural variability for the active-site loops, loop-1, loop-4 and loop-8. In the structures with inhibitor bound, the, catalytic lysine (Lys13 in loop-1) and the catalytic histidine (His95 in, loop-4) adopt conformations similar to those observed in wild-type TIM, but very different from the monoTIM structure. CONCLUSIONS: The residual, catalytic activity of monoTIM can now be rationalized. In the presence of, substrate analogues the active-site loops, loop-1, loop-4 and loop-8, as, well as the catalytic residues, adopt conformations similar to those seen, in the wild-type protein. These loops lack conformational flexibility in, wild-type TIM. The data suggest that the rigidity of these loops in, wild-type TIM, resulting from subunit-subunit contacts at the dimer, interface, is important for optimal catalysis.
About this StructureAbout this Structure
1MSS is a Single protein structure of sequence from Trypanosoma brucei brucei. Active as Triose-phosphate isomerase, with EC number 5.3.1.1 Full crystallographic information is available from OCA.
ReferenceReference
Three new crystal structures of point mutation variants of monoTIM: conformational flexibility of loop-1, loop-4 and loop-8., Borchert TV, Kishan KV, Zeelen JP, Schliebs W, Thanki N, Abagyan R, Jaenicke R, Wierenga RK, Structure. 1995 Jul 15;3(7):669-79. PMID:8591044
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