title: Elastic proteins in the flight muscle of Manduca sexta.
abstract: The flight muscles (DLM1) of the Hawkmoth, Manduca sexta are synchronous, requiring a neural spike for each contraction. Stress/strain curves of skinned DLM1 showed hysteresis indicating the presence of titin-like elastic proteins. Projectin and kettin are titin-like proteins previously identified in Lethocerus and Drosophila flight muscles. Analysis of Manduca muscles with 1% SDS-agarose gels and western blots showed two bands near 1 MDa that cross-reacted with antibodies to Drosophila projectin. Antibodies to Drosophila kettin cross-reacted to bands at ∼500 and ∼700 kDa, but also to bands at ∼1.6 and ∼2.1 MDa, that had not been previously observed in insect flight muscles. Mass spectrometry identified the 2.1 MDa protein as a product of the Sallimus (sls) gene. Analysis of the gene sequence showed that all 4 putative Sallimus and kettin isoforms could be explained as products of alternative splicing of the single sls gene. Both projectin and sallimus isoforms were expressed to higher levels in ventrally located DLM1 subunits, primarily responsible for active work production, as compared to dorsally located subunits, which may act as damped springs. The different expression levels of the 2 projectin isoforms and 4 sallimus/kettin isoforms may be adaptations to the specific requirements of individual muscle subunits.
authors.affiliation: Dept. of Biological and Chemical Sciences, Illinois Institute of Technology, 3101 S. Dearborn St., Chicago, IL 60616, USA.
authors.forename: Chen-Ching
authors.initials: CC
authors.lastname: Yuan
authors.affiliation: Dept. of Biological and Chemical Sciences, Illinois Institute of Technology, 3101 S. Dearborn St., Chicago, IL 60616, USA.
authors.forename: Weikang
authors.initials: W
authors.lastname: Ma
authors.affiliation: Dept. of Biological and Chemical Sciences, Illinois Institute of Technology, 3101 S. Dearborn St., Chicago, IL 60616, USA.
authors.forename: Peter
authors.initials: P
authors.lastname: Schemmel
authors.affiliation: Dept. of Biological and Chemical Sciences, Illinois Institute of Technology, 3101 S. Dearborn St., Chicago, IL 60616, USA.
authors.forename: Yu-Shu
authors.initials: YS
authors.lastname: Cheng
authors.affiliation: Dept. of Biological and Chemical Sciences, Illinois Institute of Technology, 3101 S. Dearborn St., Chicago, IL 60616, USA.
authors.forename: Jiangmin
authors.initials: J
authors.lastname: Liu
authors.affiliation: Center for Toxicology, University of Arizona, Tucson, AZ, USA.
authors.forename: George
authors.initials: G
authors.lastname: Tsaprailis
authors.affiliation: Dept. of Biology, College of Charleston, Charleston, SC, USA.
authors.forename: Samuel
authors.initials: S
authors.lastname: Feldman
authors.affiliation: Dept. of Biology, College of Charleston, Charleston, SC, USA.
authors.forename: Agnes
authors.initials: A
authors.lastname: Ayme Southgate
authors.affiliation: Dept. of Biological and Chemical Sciences, Illinois Institute of Technology, 3101 S. Dearborn St., Chicago, IL 60616, USA. Electronic address: irving@iit.edu.
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Irving
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D064211:Connectin / Q000032:analysis* / Q000235:genetics; D004548:Elasticity; D005426:Flight, Animal; D019476:Insect Proteins / Q000032:analysis* / Q000235:genetics; D018402:Manduca / Q000737:chemistry* / Q000235:genetics* / Q000502:physiology; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000032:analysis* / Q000235:genetics; D009132:Muscles / Q000737:chemistry / Q000502:physiology; D020033:Protein Isoforms / Q000032:analysis / Q000235:genetics; D016415:Sequence Alignment
chemical_list: D064211:Connectin; D019476:Insect Proteins; D009124:Muscle Proteins; D020033:Protein Isoforms; C078033:projectin
keywords: Elastic proteins; Insect flight muscle; Passive tension