The present invention refers to a protein-stabilized metal nanocluster comprising a variant of the helix A of the CTPR. It is also related to its uses for delivering of a drug, for interfering a metabolic reaction, for catalyzing a chemical reaction, as biocatalyst, for detecting an analyte, for phasing crystallographic data set, for cell labeling, for specific protein labeling, as biosensor, as a temperature sensor, as photosensitizer, or for the manufacture of an optoelectronic device.