The monoclonal antibodies TMH-1 and TMH-2 specifically bind to a protein encoded at the murine b-locus, not to the authentic tyrosinase encoded at the c-locus.

Three hybridomas, TMH-1, TMH-2, and TMH-3, were previously reported by Tomita et al to produce monoclonal antibodies against murine and human T4-tyrosinase localized in melanosome for the formation of melanin pigment. However, TMH antibodies were unable to react with K1735 cells transfected with the authentic tyrosinase-cDNA construct, but did react with those transfected with the pMT4-cDNA construct. The cDNA pMT4 was initially cloned as a putative tyrosinase cDNA by Shibahara et al, but it is now known to encode mouse brown (b) locus protein, which was named "tyrosinase-related protein" by Jackson or "b protein" by Hearing and Jimenez. Furthermore, TMH antibodies recognize hair bulbs of C57BL/6J-c2J/c2J mouse (B/B, c/c) lacking tyrosinase activity, but do not recognize hair bulbs of b-locus mutated DBA/2 mouse (b/b, C/C), which have authentic tyrosinase. Considering these observations, we conclude that TMH antibodies specifically recognize the protein encoded at b-locus.