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Abstract

Unconventional myosins play an important role in actin-based cell motility. Therefore, we were interested in the identification of novel mammalian myosin By screening a lambda ZAPII library (adult rat brainsem/spinal cord) with a PCR- fragment encoding a conserved region of the myosin motordomain, we identified three novel unconventional myosins, called myr 3,5 and 6. Myr 3 represents the first mammalian myosin.I closely related to Acanthamoeba and Dictyostelium myosin-Is (see Abstract by Stöffler et al.). Myr 6 can be classified as a novel member of the class V myosins. Myr 5. based on analyses of the deduced motor domain amino acid sequence, defies a novel class of myosins. contains at the 5j02kD-juction an insert of 140'amino acids is compared to the other known myosins. In the regulatory domain four IQ-myosins were detected. IQ-motifs are thought to represent light chain binding sites. The available myr 5 tail suquence is no predicted to form coiled-coil stuctrures and shows no homology to other unknown myosins. However, the tail domain of myr 5 exhibits a cysteine-rich motif possibly involved in Zne-binding and a region with homology to OTPase activating proteins such as Bcr, n-Clhimaerin, rioGAP, 3BP-1 and p190 A mRNA size of 7.5 kb was detected in various rat tissues. Polyclonal antisera which were raised against bacterially expressed myr fusion proteins recognized on immunoblots protein bands of approx. 220 kD.