ubiquitin-like protein conjugating enzyme activity +
Isoenergetic transfer of a ubiquitin-like protein (ULP) from one protein to another molecule, usually another protein, via the reaction X-SCP + Y = Y-SCP + X, where both the X-SCP and Y-SCP linkages are thioester bonds between the C-terminal amino acid of SCP and a sulfhydryl side group of a cysteine residue.