title: The Caenorhabditis elegans unc-93 gene encodes a putative transmembrane protein that regulates muscle contraction.
abstract: unc-93 is one of a set of five interacting genes involved in the regulation or coordination of muscle contraction in Caenorhabditis elegans. Rare altered-function alleles of unc-93 result in sluggish movement and a characteristic "rubber band" uncoordinated phenotype. By contrast, null alleles cause no visibly abnormal phenotype, presumably as a consequence of the functional redundancy of unc-93. To understand better the role of unc-93 in regulating muscle contraction, we have cloned and molecularly characterized this gene. We isolated transposon-insertion alleles and used them to identify the region of DNA encoding the unc-93 protein. Two unc-93 proteins differing at their NH2 termini are potentially encoded by transcripts that differ at their 5' ends. The putative unc-93 proteins are 700 and 705 amino acids in length and have two distinct regions: the NH2 terminal portion of 240 or 245 amino acids is extremely hydrophilic, whereas the rest of the protein has multiple potential membrane-spanning domains. The unc-93 transcripts are low in abundance and the unc-93 gene displays weak codon usage bias, suggesting that the unc-93 protein is relatively rare. The unc-93 protein has no sequence similarity to proteins listed in current data-bases. Thus, unc-93 is likely to encode a novel membrane-associated muscle protein. We discuss possible roles for the unc-93 protein either as a component of an ion transport system involved in excitation-contraction coupling in muscle or in coordinating muscle contraction between muscle cells by affecting the functioning of gap junctions.
authors.affiliation: Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.
authors.forename: J Z
authors.initials: JZ
authors.lastname: Levin
authors.forename: H R
authors.initials: HR
authors.lastname: Horvitz
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002107:Caenorhabditis / Q000235:genetics / Q000502:physiology*; D029742:Caenorhabditis elegans Proteins; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics / Q000302:isolation & purification / Q000528:radiation effects; D004251:DNA Transposable Elements; D005091:Exons; D005720:Gamma Rays; D015723:Gene Library; D015321:Gene Rearrangement; D015801:Helminth Proteins / Q000235:genetics*; D007438:Introns; D008565:Membrane Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D009119:Muscle Contraction; D009124:Muscle Proteins / Q000235:genetics* / Q000502:physiology; D016254:Mutagenesis, Insertional; D011110:Polymorphism, Genetic; D011487:Protein Conformation; D012091:Repetitive Sequences, Nucleic Acid; D015183:Restriction Mapping; D014158:Transcription, Genetic
chemical_list: D029742:Caenorhabditis elegans Proteins; D004251:DNA Transposable Elements; D015801:Helminth Proteins; D008565:Membrane Proteins; D009124:Muscle Proteins; C073904:unc-93 protein, C elegans; D004247:DNA