Date of Award

Fall 1991

Degree Type

Thesis - Restricted

Degree Name

Master of Science (MS)

Department

Biology

Abstract

Two smooth muscle myosin heavy chains [MHC, SM1, approximately 205 kilodaltons (KD), and SM2, approximately 200 KD] were separated on sodium dodecyl sulfate (SDS)polyacrylamide gels. The difference between these two heavy chains lies in the light meromyosin (LM) fragment which is the tail fragment of the molecule (Eddinger and Murphy, 1988; Nagai et al., 1989). In order to determine the MHC composition in smooth muscle tissue, the native myosin molecule (composed of two MHC's) was purified from the stomach tissue of swine and rabbit. MHC composition was inferred from analysis of the association of the LM fragment from purified myosin. Limited chymotryptic digestion of purified smooth muscle tissues produced two LM fragments from the two MHC's (LM1 from SM1 and LM2 from SM2, approximately 100 and 95 KD, respectively). When the native LM was oxidized and run on a non-reducing SDS gel three bands were observed which migrated at approximately 200, 195 and 190 KD. Excision of these bands and electrophoresis on a reducing SDS gel showed their subunit composition. The upper band was composed solely of LM1. The middle band was composed of an equal ratio of LM1 and LM2 and the bottom band was composed solely of LM2. Western blotting analysis using MHC specific antibodies also confirmed the composition of each band from reducing SDS gels. These results indicate that three myosin isoforms exist in smooth muscle cells with respect to MHC composition as the SMl homodimer, the SM1-SM2 heterodimer and the SM2 homodimer.

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