Complex sentence: Although cysteine also has a nucleophilic sulfur atom, the peptide bond following this amino acid is not cleaved because the cyanide adduct rapidly deprotonates, leaving the sulfur center uncharged and the beta carbon of the cysteine not electrophilic.
Split into simpler sentences: Although cysteine also has a nucleophilic sulfur atom, the peptide bond following this amino acid is not cleaved. This is because the cyanide adduct becomes rapidly deprotonated, leaving the sulfur uncharged and the beta carbon of the cysteine not electrophilic.