Arg158

Arg158 denotes the arginine residue located at position 158 in a protein sequence or structure. It is identified by the three-letter code Arg (or the one-letter code R) together with the position number, and the exact identity and role of Arg158 can vary between proteins.

The residue numbering that assigns Arg158 depends on the specific protein, isoform, or processing state, and sometimes differs between sequence databases and structural models. In many contexts, Arg158 is simply one reference point among many used to discuss structure-function relationships in a given protein.

In proteins, arginine residues are positively charged at physiological pH and commonly participate in electrostatic interactions, hydrogen bonding, and coordination of substrates or cofactors. Arg158 can contribute to active-site geometry, stabilize negative charges, or help mediate protein–protein or protein–nucleic acid interactions when situated in a compatible structural context. Substituting Arg158 with other residues (for example, to alanine, lysine, or glutamate) can disrupt salt bridges or hydrogen bonds, potentially altering stability, binding affinity, or catalytic activity, and such substitutions are frequently explored in site-directed mutagenesis studies.

Conservation of Arg158 within a protein family may indicate a functional or structural role, though this is not universal and varies by protein. When consulting literature or databases, it is important to verify the residue numbering used, as different sources may index the same residue differently due to isoforms, processing, or modeling conventions.

Related topics include residue numbering conventions, the amino acid arginine, and approaches to site-directed mutagenesis.