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Function of your protein

The function of this protein is an L-amino acid that involved in Staphylococcal sulfur amino acid metabolism. The role of this amino protein is that predominately catalyze the ATP Ligation of various carboxylate and amine substrates.

LdmS is a ligase enzyme that catalyzes the formation of a peptide bond between L-aspartate and L-methionine to produce the dipeptide L-Asp-L-Met. This reaction is the first step in the biosynthesis of the antibiotic. Therefore, LdmS is specific to L-aspartate and L-methionine as substrates and produces L-Asp-L-Met as the product.

Biological relevance and broader implications

    This paper emphasizes the biological significance of the protein LdmS, which is found in bacteria. The protein's importance lies in its potential as a target for developing antibiotics. It is predominantly found in gram-positive bacteria, which are known to cause various infections. Understanding the structure and function of LdmS is crucial in the fight against antibiotic resistance. Hence, this protein holds immense importance in the scientific community as it presents a promising avenue for the development of novel antibiotics.
   

Important amino acids

The ligand for this molecule is ADP: ADENOSINE-5'-DIPHOSPHATE .

The residues N255, D288, and S309 form the catalytic triad in LdmS. N255 and D288 are involved in coordinating the divalent metal ion, while S309 is responsible for activating the nucleophile. This triad plays a crucial role in the formation of the ʟ-aspartate-ʟ-methionine bond.

The residues R305 and G308 are also important for the protein's function. R305 is involved in stabilizing the transition state during catalysis, while G308 helps to position the P-loop and N-loop motifs in the active site. The P-loop and N-loop motifs are essential for binding the substrates and coordinating the divalent metal ion, respectively.

Structural highlights

These secondary structural features are important for stabilizing the overall structure of the LdmS protein and also play a role in protein interactions or ligand binding. For example, alpha helices form amphipathic surfaces that interact with lipid membranes or other proteins, while beta strands form beta sheets that provide structural rigidity and can also participate in hydrogen bonding with ligands.

The tertiary structure of the protein refers to the three-dimensional arrangement of its secondary structural elements as you can see here in the image and is determined by the interactions between amino acid side chains and the protein backbone. A polar cavity is formed by the sidechains of Gln244, Tyr252, Asn255, Asn307, and Ser309, and the backbone of Gly308 and Ser309. A hydrophobic cavity is also formed upon closure of the P-loop and N-loop, comprised of Pro26, Leu34, Pro36, Leu44, Tyr111, Ala181, and Tyr184, with the guanidinium sidechain of Arg47 positioned below the cavity opening.

The quaternary structure refers to the arrangement of multiple protein subunits into a larger complex and can play a role in modulating protein function. In this case, the presence of two subunits may enable cooperative binding of ligands or other proteins to the enzyme's active site.

Here is a space-filling view of the protein, which provides information about the three-dimensional arrangement of amino acid side chains and the overall shape of the protein. This can be important for understanding protein function, as certain domains or regions of the protein may be more exposed and accessible to ligands or other proteins. In this example, the cleft between the two subunits represents the active site of the enzyme, which may be important for substrate binding and catalysis. Additionally, the presence of large loops or domains on the surface of the protein may be indicative of regions that play a role in protein-protein interactions or signaling. To be specific two large loop regions in this paper are, the P-loop (Res. 175–186) and an N-terminal loop region, herein referred to as the N-loop (Res. 28–38).

Other important features

Conserved Motifs: LdmS contains two highly conserved motifs, the P-loop motif and the N-loop motif. These motifs are commonly found in ATP-binding proteins and are involved in binding and hydrolysis of ATP. The P-loop motif is responsible for binding the phosphate groups of ATP, while the N-loop motif helps in stabilizing the ADP molecule after hydrolysis. The presence of these motifs in LdmS suggests that the protein utilizes ATP as a cofactor in its enzymatic activity. Figure 1 from the paper shows the crystal structure of LdmS highlighting the location of the P-loop and N-loop motifs. The P-loop motif is shown in red, while the N-loop motif is shown in purple

Dimerization Interface: LdmS exists as a dimer in solution, and dimerization is critical for its enzymatic activity. The dimerization interface involves the formation of a β-sheet between two monomers, which creates a cleft that accommodates the ligand-binding site. The dimerization interface also helps to stabilize the protein structure and protect the active site from solvent exposure.

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