Avidin related protein 2 shows unique structural and functional features among the avidin protein family

Background  

The chicken avidin gene family consists of avidin and several avidin related genes (AVRs). Of these gene products, avidin is the best characterized and is known for its extremely high affinity for D-biotin, a property that is utilized in numerous modern life science applications. Recently, the AVR genes have been expressed as recombinant proteins, which have shown different biotin-binding properties as compared to avidin.     

The Genes for Mouse Salivary Androgen-Binding Protein (Abp) Subunits Alpha and Gamma Are Located on Chromosome 7

We demonstrate that the previously described gene Androgen binding protein (Abp; Dlouhy and Karn, 1984) codes for the Alpha subunit of ABP and rename the locus Androgen binding protein alpha (Abpa). A study of recombinant inbred strains demonstrates that Abpa is located on chromosome 7 near Glucose phosphate isomerase-1 (Gpi-1). Biochemical and genetic evidence indicates the existence of another ABP subunit, Gamma, and its locus, Androgen binding protein gamma (Abpg), that is closely linked to Abpa. Although no polymorphism has yet been found for the previously described Beta subunit of ABP (Dlouhy and Karn, 1983; 1984), we suggest that it represents a third locus. Androgen binding protein beta (Abpb). ABP subunits appear to dimerize randomly and a model is presented demonstrating the origin of six ABP dimers in the salivas of AbpaaAbpga/AbpabAbpgb heterozygous mice. The results of cell-free translation studies in which the pre-ABP subunits are identified specifically by immunoprecipitation with anti-ABP antibody supports the idea that independent mRNAs code for the Alpha, Beta and Gamma subunits.     

Paramyosin gene (unc-15) of Caenorhabditis elegans. Molecular cloning, nucleotide sequence and models for thick filament structure

Paramyosin is a major structural component of thick filaments isolated from many invertebrate muscles. The Caenorhabditis elegans paramyosin gene (unc-15) was identified by screening with specific antibodies an "exon-expression" library containing lacZ/nematode gene fusions. Short probes recovered from the library were used to identify bacteriophage lambda and cosmid clones that encompass the entire paramyosin (unc-15) gene. From these clones, numerous subclones containing epitopes reacting with anti-paramyosin sera were obtained, providing strong evidence that the initial cloned fragment was, in fact, derived from the structural gene for paramyosin. The complete nucleotide sequence of a 12 x 10(3) base-pair region spanning the gene was obtained. The gene is composed of ten short exons encoding a protein of 866 [corrected] amino acid residues. Paramyosin is highly similar to residues 267 to 1089 of myosin heavy chain rods. For most of its length, paramyosin appears to form an alpha-helical coiled-coil and shows the expected heptad repeat of hydrophobic amino acid residues and the 28-residue repeat of charged amino acids characteristic of myosin heavy chain rods. However, paramyosin differs from myosin in having non-helical extensions at both the N and C termini and an additional "skip" residue that interrupts the 28-residue repeat. The distribution of charges along the length of the paramyosin rod is also significantly different from that of myosin heavy chain rods. Potential charge-mediated interactions between paramyosin rods and between paramyosin and myosin rods were calculated using a model successfully applied previously to the analysis of the myosin rod sequences. Myosin rods aligned in parallel show optimal charge-charge interactions at multiples of 98 residue staggers (i.e. at axial displacements of multiples of 143 A). Paramyosin rods, in contrast, appear to interact optimally at parallel staggers of 493 residues (i.e. at axial displacements of 720 A) but show only weak interaction peaks at 98 or 296 residues. Similar calculations suggest optimal interactions between paramyosin molecules and myosin rods and in their anti-parallel alignments. The implications of these results for the structure of the bare zone and the assembly of nematode thick filaments are discussed.     

Sex-limited effects of the expression of the db gene in mice during puberty

The autosomal recessive gene diabetes (db) produces a condition similar to human insulin-dependent diabetes mellitus in certain strains of inbred mice. In this investigation, the effects of expression of the db gene on the development of the submandibular glands, electrophoretic protein patterns in salivas, fasting blood glucose levels, and glycosylated hemoglobin levels were evaluated in mice undergoing puberty. Three sex-limited effects of the db gene were observed in diabetic male mice: (1) a compromise of the development of the specialized submandibular glands with the extensive tubular portion normally found in males, (2) failure to develop a salivary protein pattern unique to male mice, and (3) attainment of higher levels of fasting blood glucose than found in female diabetic mice. Since it has been documented that homozygous mice fail to develop functional gonads, apparently due to insufficient production of gonadotropin, it is likely that the compromised development of the specialized submandibular glands, and, consequently, the male salivary protein pattern, is a result of decreased testosterone production. Experiments in which diabetic mice were treated with testosterone support that conclusion, since testosterone caused transformation of the salivary protein pattern to one identical with that of normal male littermate controls and increased the tubular portion of the submandibular glands.This study was supported in part by Public Health Service Research Grant 5 R01 AM21177 and by the Indiana University Human Genetics Center (PHS P01 GM21054). The author was supported by Public Health Service Career Development Award 1 K04 AM00284. This is Publication No. 79-18 from the Indiana University Human Genetics Center.