title: Evolution of long-range myofibrillar crystallinity in insect flight muscle as examined by X-ray cryomicrodiffraction.
abstract: Insect flight muscle is known for its crystal-quality regularity of contractile protein arrangement within a sarcomere. We have previously shown by X-ray microdiffraction that the crystal-quality regularity in bumble-bee flight muscle is not confined within a sarcomere, but extends over the entire length of a myofibril (>1000 sarcomeres connected in series). Because of this, the whole myofibril may be regarded as a millimetre-long, natural single protein crystal. Using bright X-ray beams from a synchrotron radiation source, we examined how this long-range crystallinity has evolved among winged insects. We analysed >4600 microdiffraction patterns of quick-frozen myofibrils from 50 insect species, covering all the major winged insect orders. The results show that the occurrence of such long-range crystallinity largely coincides with insect orders with asynchronous muscle operation. However, a few of the more skilled fliers among lower-order insects apparently have developed various degrees of structural regularity, suggesting that the demand for skillful flight has driven the lattice structure towards increased regularity.
authors.affiliation: Research Institute Research and Utilization Division, SPring-8, Japan Synchrotron Radiation, Sayo-gun, Hyogo 679-5198, Japan. iwamoto@spring8.or.jp
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Iwamoto
authors.forename: Katsuaki
authors.initials: K
authors.lastname: Inoue
authors.forename: Naoto
authors.initials: N
authors.lastname: Yagi
mesh_terms: D000818:Animals; D005426:Flight, Animal; D007313:Insecta / Q000033:anatomy & histology* / Q000648:ultrastructure; D018482:Muscle, Skeletal / Q000737:chemistry / Q000648:ultrastructure*; D009210:Myofibrils / Q000737:chemistry / Q000648:ultrastructure*; D014961:X-Ray Diffraction / Q000379:methods