title: Preserved close linkage between the genes encoding troponin I and troponin T, reflecting an evolution of adapter proteins coupling the Ca(2+) signaling of contractility.
abstract: Ca(2+)-regulated motility is essential to numerous cellular functions, including muscle contraction. Systems with troponin C, myosin light chain, or calmodulin as the Ca(2+) receptor have evolved in striated muscle and other types of cells to transduce the cytoplasm Ca(2+) signals into allosteric conformational changes of contractile proteins. While these Ca(2+) receptors are homologous proteins, their coupling to the responding elements is quite different in various cell types. The Ca(2+) regulatory system in vertebrate striated muscle represents a highly specialized such signal transduction pathway consisting of the troponin complex and tropomyosin associated with the actin filament. To understand the molecular mechanism in the Ca(2+) regulation of muscle contraction and cell motility, we have revealed a preserved ancestral close linkage between the genes encoding two of the troponin subunits, troponin I and troponin T, in the genome of mouse. The data suggest that the troponin I and troponin T genes may have originated from a single locus and evolved in parallel to encode a striated muscle-specific adapter to couple the Ca(2+) receptor, troponin C, to the actin-myosin contractile machinery. This hypothesis views the three troponin subunits as two structure-function domains: the Ca(2+) receptor and the signal transducing adapter. This model may help to further our understanding of the Ca(2+) regulation of muscle contraction and the structure-function relationship of other potential adapter proteins which are converged to constitute the Ca(2+) signal transduction pathways governing nonmuscle cell motility.
authors.affiliation: Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106-4970, USA.
authors.forename: Q Q
authors.initials: QQ
authors.lastname: Huang
authors.forename: J P
authors.initials: JP
authors.lastname: Jin
mesh_terms: D000375:Aging; D000818:Animals; D020013:Calcium Signaling / Q000235:genetics*; D019143:Evolution, Molecular; D005786:Gene Expression Regulation / Q000235:genetics; D017930:Genes, Reporter / Q000235:genetics; D008040:Genetic Linkage / Q000235:genetics*; D016678:Genome; D051379:Mice; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000196:embryology / Q000378:metabolism; D009200:Myocardial Contraction; D009206:Myocardium / Q000378:metabolism; D020161:Physical Chromosome Mapping; D011401:Promoter Regions, Genetic / Q000235:genetics; D013329:Structure-Activity Relationship; D019210:Troponin I / Q000235:genetics* / Q000378:metabolism; D020107:Troponin T / Q000235:genetics* / Q000378:metabolism
chemical_list: D019210:Troponin I; D020107:Troponin T