The nature of chemical bonding and its effect on spin-polarized electron transport in Ni-C-60-Ni are studied using density functional theory in conjunction with the Landauer-Buttiker formalism. The binding site on the C-60 cage surface appears to have a strong influence on the electron tunneling current between Ni leads. The tunnel current has a much higher magnitude when Ni is bonded to hole sites (H6, H5) than at bridge sites (B66, B56) of the fullerene cage. Furthermore, the magnitude of junction magnetoresistance is predicted to be significantly high for the molecular Ni-C-60-Ni system. (c) 2007 Elsevier B.V. All rights reserved.