Publications

• Antenna domain mobility and enzymatic reaction of L-rhamnulose-1-phosphate aldolase.

  Grueninger D., Schulz G.E.

  The enzyme l-rhamnulose-1-phosphate aldolase from Escherichia coli participates in the degradation pathway of l-rhamnose, a ubiquitous deoxy-hexose. It is a homotetramer of the rare C4-symmetric type with N-terminal domains protruding like antennas from the main body. A mobility analysis of the en ... >> More

  The enzyme l-rhamnulose-1-phosphate aldolase from Escherichia coli participates in the degradation pathway of l-rhamnose, a ubiquitous deoxy-hexose. It is a homotetramer of the rare C4-symmetric type with N-terminal domains protruding like antennas from the main body. A mobility analysis of the enzyme gave rise to the hypothesis that an anisotropic thermal antenna motion may support the catalysis (Kroemer et al., Biochemistry 42, 10560, 2003). We checked this hypothesis by generating four single mutants and one disulfide bridge that were designed to reduce the mobility of the antenna domain without disturbing the chain-fold or the active center. The catalytic rates of the mutants revealed activity reductions that correlated well with the expected antenna fixation. Among these mutants, K15W was crystallized, structurally elucidated, and used as a guide for modeling the others. The structure confirmed the design because the mutation introduced a tight nonpolar contact to a neighboring subunit that fixed the antenna but did not affect the main chain. The fixation was confirmed by a comparison of the anisotropic B-factors describing the mobility of the domains. It turned out that the distinctly anisotropic mobility of the wild-type antenna domain has become isotropic in K15W, in agreement with the design. We suggest that, like K15W, the other mutations also followed the design, validating the correlation between antenna mobility and activity. This correlation suggests that the domain mobility facilitates the reaction. << Less

  Biochemistry 47:607-614(2008) [PubMed] [EuropePMC]

• Structure and catalytic mechanism of L-rhamnulose-1-phosphate aldolase.

  Kroemer M., Merkel I., Schulz G.E.

  The structure of L-rhamnulose-1-phosphate aldolase has been established at 1.35 A resolution in a crystal form that was obtained by a surface mutation and has one subunit of the C(4)-symmetric tetramer in the asymmetric unit. It confirms an earlier 2.7 A resolution structure which was determined i ... >> More

  The structure of L-rhamnulose-1-phosphate aldolase has been established at 1.35 A resolution in a crystal form that was obtained by a surface mutation and has one subunit of the C(4)-symmetric tetramer in the asymmetric unit. It confirms an earlier 2.7 A resolution structure which was determined in a complicated crystal form with 20 subunits per asymmetric unit. The chain fold and the active center are similar to those of L-fuculose-1-phosphate aldolase and L-ribulose-5-phosphate 4-epimerase. The active center similarity is supported by a structural comparison of all three enzymes and by the binding mode of the inhibitor phosphoglycolohydroxamate at the site of the product dihydroxyacetone phosphate for the two aldolases. The sensitivity of the catalytic rate to several mutations and a comparison with the established mechanism of the related aldolase give rise to a putative catalytic mechanism. This mechanism involves the same binding mode of the second product L-lactaldehyde in both aldolases, except for a 180 degrees flip of the aldehyde group distinguishing between the two epimers rhamnulose and fuculose. The N-terminal domain exhibits a correlated anisotropic mobility that channels the isotropic Brownian motion into a directed movement of the catalytic base and the substrate phosphate on the N-domain toward the zinc ion and the lactaldehyde on the C-terminal domain. We suggest that this movement supports the catalysis mechanically. << Less

  Biochemistry 42:10560-10568(2003) [PubMed] [EuropePMC]