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See detailStructural basis for the actin-binding function of missing-in-metastasis.
Lee, Sung Haeng; Kerff, Frédéric ULg; Chereau, David et al

in Structure (2007), 15(2), 145-55

The adaptor protein missing-in-metastasis (MIM) contains independent F- and G-actin binding domains, consisting, respectively, of an N-terminal 250 aa IRSp53/MIM homology domain (IMD) and a C-terminal ... [more ▼]

The adaptor protein missing-in-metastasis (MIM) contains independent F- and G-actin binding domains, consisting, respectively, of an N-terminal 250 aa IRSp53/MIM homology domain (IMD) and a C-terminal WASP-homology domain 2 (WH2). We determined the crystal structures of MIM's IMD and that of its WH2 bound to actin. The IMD forms a dimer, with each subunit folded as an antiparallel three-helix bundle. This fold is related to that of the BAR domain. Like the BAR domain, the IMD has been implicated in membrane binding. Yet, comparison of the structures reveals that the membrane binding surfaces of the two domains have opposite curvatures, which may determine the type of curvature of the interacting membrane. The WH2 of MIM is longer than the prototypical WH2, interacting with all four subdomains of actin. We characterize a similar WH2 at the C terminus of IRSp53 and propose that in these two proteins WH2 performs a scaffolding function. [less ▲]

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See detailCrystal structure of a D-aminopeptidase from Ochrobactrum anthropi, a new member of the 'penicillin-recognizing enzyme' family.
Bompard-Gilles, C.; Remaut, H.; Villeret, V. et al

in Structure (2000), 8(9), 971-80

BACKGROUND: beta-Lactam compounds are the most widely used antibiotics. They inactivate bacterial DD-transpeptidases, also called penicillin-binding proteins (PBPs), involved in cell-wall biosynthesis ... [more ▼]

BACKGROUND: beta-Lactam compounds are the most widely used antibiotics. They inactivate bacterial DD-transpeptidases, also called penicillin-binding proteins (PBPs), involved in cell-wall biosynthesis. The most common bacterial resistance mechanism against beta-lactam compounds is the synthesis of beta-lactamases that hydrolyse beta-lactam rings. These enzymes are believed to have evolved from cell-wall DD-peptidases. Understanding the biochemical and mechanistic features of the beta-lactam targets is crucial because of the increasing number of resistant bacteria. DAP is a D-aminopeptidase produced by Ochrobactrum anthropi. It is inhibited by various beta-lactam compounds and shares approximately 25% sequence identity with the R61 DD-carboxypeptidase and the class C beta-lactamases. RESULTS: The crystal structure of DAP has been determined to 1.9 A resolution using the multiple isomorphous replacement (MIR) method. The enzyme folds into three domains, A, B and C. Domain A, which contains conserved catalytic residues, has the classical fold of serine beta-lactamases, whereas domains B and C are both antiparallel eight-stranded beta barrels. A loop of domain C protrudes into the substrate-binding site of the enzyme. CONCLUSIONS: Comparison of the biochemical properties and the structure of DAP with PBPs and serine beta-lactamases shows that although the catalytic site of the enzyme is very similar to that of beta-lactamases, its substrate and inhibitor specificity rests on residues of domain C. DAP is a new member of the family of penicillin-recognizing proteins (PRPs) and, at the present time, its enzymatic specificity is clearly unique. [less ▲]

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See detailA new variant of the Ntn hydrolase fold revealed by the crystal structure of L-aminopeptidase D-ala-esterase/amidase from Ochrobactrum anthropi.
Bompard-Gilles, C; Villeret, V; Davies, G J et al

in Structure (2000), 8(2), 153-62

BACKGROUND: The L-aminopeptidase D-Ala-esterase/amidase from Ochrobactrum anthropi (DmpA) releases the N-terminal L and/or D-Ala residues from peptide substrates. This is the only known enzyme to liberate ... [more ▼]

BACKGROUND: The L-aminopeptidase D-Ala-esterase/amidase from Ochrobactrum anthropi (DmpA) releases the N-terminal L and/or D-Ala residues from peptide substrates. This is the only known enzyme to liberate N-terminal amino acids with both D and L stereospecificity. The DmpA active form is an alphabeta heterodimer, which results from a putative autocatalytic cleavage of an inactive precursor polypeptide. RESULTS: The crystal structure of the enzyme has been determined to 1.82 A resolution using the multiple isomorphous replacement method. The heterodimer folds into a single domain organised as an alphabetabetaalpha sandwich in which two mixed beta sheets are flanked on both sides by two alpha helices. CONCLUSIONS: DmpA shows no similarity to other known aminopeptidases in either fold or catalytic mechanism, and thus represents the first example of a novel family of aminopeptidases. The protein fold of DmpA does, however, show structural homology to members of the N-terminal nucleophile (Ntn) hydrolase superfamily. DmpA presents functionally equivalent residues in the catalytic centre when compared with other Ntn hydrolases, and is therefore likely to use the same catalytic mechanism. In spite of this homology, the direction and connectivity of the secondary structure elements differ significantly from the consensus Ntn hydrolase topology. The DmpA structure thus characterises a new subfamily, but supports the common catalytic mechanism for these enzymes suggesting an evolutionary relationship. [less ▲]

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See detailStructures of the psychrophilic Alteromonas haloplanctis a-amylase give insights into cold adaptation at a molecular level
Aghajari, N.; Feller, Georges ULg; Gerday, Charles ULg et al

in Structure (1998), 6

Background: Enzymes from psychrophilic (cold-adapted) microorganisms operate at temperatures close to 0 degrees C, where the activity of their mesophilic and thermophilic counterparts is drastically ... [more ▼]

Background: Enzymes from psychrophilic (cold-adapted) microorganisms operate at temperatures close to 0 degrees C, where the activity of their mesophilic and thermophilic counterparts is drastically reduced. It has generally been assumed that thermophily is associated with rigid proteins, whereas psychrophilic enzymes have a tendency to be more flexible. Results: Insights into the cold adaptation of proteins are gained on the basis of a psychrophilic protein's molecular structure. To this' end, we have determined the structure of the recombinant form of a psychrophilic a-amylase from Alteromonas haloplanctis at 2.4 Angstrom resolution. We have compared this with the structure of the wild-type enzyme, recently solved at 2.0 Angstrom resolution, and with available structures of their mesophilic counterparts. These comparative studies have enabled us to identify possible determinants of cold adaptation. Conclusions: We propose that an increased resilience of the molecular surface and a less rigid protein core, with less interdomain interactions, are determining factors of the conformational flexibility that allows efficient enzyme catalysis in cold environments. [References: 57] 57 [less ▲]

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