GO:0061604:   molybdopterin-synthase sulfurtransferase activity
Catalysis of the reaction: [Molybdopterin-synthase sulfur-carrier protein]-Gly-Gly-AMP + [cysteine desulfurase]-S-sulfanyl-L-cysteine <=> AMP [molybdopterin-synthase sulfur-carrier protein]-Gly-NH-CH(2)-C(O)SH + cysteine desulfurase.