G3DxxG

G3DxxG is a shorthand notation used in protein sequence analysis to describe a short, degenerate amino acid motif. In this pattern, the first residue is glycine (G), followed by three unspecified amino acids, then aspartate (D), followed by two more unspecified residues, and ending with glycine (G). The x represents any amino acid, while the numerical prefix indicates the number of variable positions between the specified residues.

Motifs like G3DxxG are used in motif discovery and annotation workflows to scan protein sequences for candidate functional sites. G3DxxG can be detected by regular-expression searches or by probabilistic models such as position-specific scoring matrices and hidden Markov models. Because the motif is degenerate, a single protein sequence can contain multiple matches, and many matches may be nonfunctional or context-dependent.

The term is employed as a descriptive pattern rather than a universally validated motif; occurrences have been reported across diverse protein families in computational studies. It is not tied to a single enzymatic activity or structural role and should be interpreted with structural data and broader sequence context.

Applications include aiding functional annotation, guiding site-directed mutagenesis, and informing structure–function analyses. Limitations include the potential for false positives, sensitivity to alignment errors, and dependence on the quality of the underlying motif model. Researchers typically corroborate G3DxxG hits with experimental data or structural insight.