Myosin Binding Protein-C Slow: An Intricate Subfamily of Proteins
Figure 3
Western blot analysis of protein homogenates prepared from rat skeletal muscles and blotted with antibodies to the fifth Ig domain that recognize all MyBP-C slow variants (a) or to the novel COOH-terminal insertion that specifically recognizes variant 1 (b). (a) Top panel: With the exception of quadriceps, all other muscles express variant 1, represented by the upper most band, marked by a blue dot. All adult skeletal muscles tested, but not the developing myofibers, express variants 2 and/or 3, corresponding to the band with the intermediate mobility, and denoted with a red dot. As variants 2 and 3 have similar molecular weights (129 and 128 kDa, respectively), it is not feasible to separate them in the current gel system. Moreover, variant 4 is detected in homogenates prepared from EDL, FDB, gastrocnemious, and soleus, and is represented by the lower immunoreactive band, marked with a green dot. Bottom panel: A cartoon showing the presence of the different MyBP-C slow variants in developing and adult skeletal muscles. Dotted lines correspond to immunoreactive bands, which are evident only after long exposure times. (b) In agreement with the immunoblot shown in panel (a), antibodies specific for the novel COOH-terminal insert demonstrated that EDL, FDB, TA, gastrocnemious, soleus, and P1 skeletal myotubes express variant 1, with soleus containing the highest amounts.
