Protein structural homology: a metric approach

The flexibility of the polypeptide fold of proteins is essentially due to the rotational freedom about the main chain bonds involving C alpha atoms. The polypeptide fold can therefore be represented by virtual bonds joining consecutive C alpha atoms. The ordered sequence of virtual torsion and bond angles involving these bonds can be used to specify the fold. Such representations can then be compared to reveal structural similarities using the Needleman & Wünsch algorithm, which has been developed for comparison of amino acid sequences. Such an approach is presented and illustrated with examples. The method is suitable for detecting structural similarities that extend over 7 or more residues.     

A colorimetric micro method for the determination of formyl groups

The characteristic purple colour formed by N-formyl-N'-2,4-dinitrophenyl-hydrazine in the presence of piperidine and acetone was made the basis of a new quantitative method for the determination of formyl groups. Samples containing N-formyl groups (up to 0.4mumole) are hydrazinolysed at 97-98 degrees for 1hr. and are dinitrophenylated after the removal of excess of hydrazine. Interference from 2,4-dinitrophenylhydrazine is eliminated by subjecting the dinitrophenylated samples to chromatography on an alumina column. Interference arising from the formation of N-acetyl-N'-2,4-dinitrophenylhydrazine, when determining formyl groups in samples containing acetyl, can be avoided by a paper-chromatographic separation before analysis. A standard procedure is described. The method gives satisfactory results when applied to N-formyl-amino acids. Gramicidin, when analysed by this method, was found to contain 0.89 mole of formyl group/mole for a molecular weight of 1880. The method indicated the absence of formyl groups from lysozyme, a protein known not to contain such groups. Generally, the analytical values obtained by the method are within 100+/-4% of theory.     

Prionospio atrovitta (Annelida: Spionidae), a new species from Andaman and Nicobar archipelago,northern Indian Ocean

ABSTRACT

A new species of polychaete, Prionospio atrovitta, is described from the sandy sediments of the Andaman and Nicobar insular margin. The major feature distinguishing P. atrovitta from other species of the genus Prionospio is the presence of well-marked black pigmented band near the anterior dorsal margin of the prostomium and pigmentation on the caruncle in the adults.     

Creatine kinase/α-crystallin interaction functions in cataract development

Creatine kinase (CK) is an energy storage enzyme that plays an important role in energy metabolism. CK/phosphocreatine functions as an energy buffer and links ATP production sites with ATP utilization sites. Several key mutations in the αA-crystallin (cryaa) and αB-crystallin (cryab) genes have been linked with autosomal-dominant, hereditary human cataracts. The cryaa-R49C mutation was identified in a four-generation Caucasian family. We previously identified an increase in the quantity of CK complexed with α-crystallin in the lenses of knock-in mice expressing the cryaa-R49C mutation using proteomic analyses. Increased levels of CK in postnatal cataractous lenses may indicate increased ATP requirements during early cataract development. To gain a further understanding of the relationship between CK and α-crystallin, we investigated whether α-crystallin interacts with and forms complexes with CK, in vitro. Isothermal titration calorimetry (ITC) showed that each CK dimer bound to 28 α-crystallin subunits, with a K_d of 3.3 × 10^?7 M, and that the interaction between α-crystallin and CK was endothermic, thermodynamically favorable, and entropy-driven. High-salt concentrations did not affect the interaction between CK and α-crystallin, suggesting that the interaction between CK and α-crystallin is primarily hydrophobic. Gel permeation chromatography (GPC) detected water-soluble α-crystallin and CK complexes, as determined by increased light scattering after complex formation. In addition, CK and α-crystallin formed partially-water-insoluble, high-molecular-mass complexes. Enzyme-linked immunosorbent assay (ELISA)-based enzymatic activity analyses of lens homogenates showed a 17-fold increase in CK activity in the postnatal lenses of cryaa-R49C knock-in mice. These studies indicate that the interaction between α-crystallin and CK is functionally important and that increased CK levels may be necessary to meet the increased ATP demands of ATP-dependent functions in cataractous lenses.     

The response ofRhizobium meliloti to L-methionine DL-sulphoximine

A strain ofRhizobium meliloti has been shown to be capable of growth in the presence of methionine sulphoximine concentrations at least two orders of magnitude higher than that required for the complete inhibition of glutamine synthetase activity. Neither the specific growth rate, nor the nutritional requirements of the organism were affected by methionine sulphoximine in the medium.Rhizobium meliloti appeared to assimilate ammoniavia the glutamate dehydrogenase pathway during growth in the presence of methionine sulphoximine. This suggests thatRhizobium meliloti may have some regulatory mechanism controlling ammonia assimilation that is not present in other enterobacteria possessing similar enzymatic machinery     

Some characteristics of the normal menstrual cycle of the bonnet monkey (M. radiata)

Sixty-two menstrual cycles were observed in five bonnet monkeys over a period of 12 months. The menstrual cycles ranged in length from 22 to 35 days, although cycles of from 26 to 29 days were most frequent. Menstrual flow occurred for two to seven days, the flow lasting for three to four days in the majority (82%) of the cycles. Serum estradiol-17β (E₂) and progesterone (P) were measured by radioimmunoassay in two consecutive cycles in each monkey and correlated with changes in the quantity of cervical mucus secretion and spinnbarkeit. The day of the estradiol peak was considered as day 0. The E₂ levels began to rise one to three days before the peak, returning to baseline levels within two days and thereafter remained at low levels. The serum P rose 2 days after the E₂ peak, and maximum level was attained at 10 to 12 days after the E₂ peak. The quantity of cervical mucus increased proportionately with estrogen. However, the quantity remained at maximum levels even after the decline of the serum E₂ level. Similar trends were observed with the spinnbarkeit.     

Probability of random sire exclusion using microsatellite markers for parentage verification

Many microsatellite sequences have been described in the bovine genome. Being highly polymorphic these have been suggested as markers for parentage verification and individual identification in cattle. We have evaluated the use of five highly polymorphic microsatellite markers for parentage verification in 14 breeds of cattle in the UK. Three of the microsatellite loci occur within introns in genes: BoLA DRB3 , steroid 21-hydroxylase, and the beta subunit of the follicle-stimulating hormone. The other two are anonymous sites ETH131 and HEL6. Results were analysed by a statistical approach that takes in to account deviations from Hardy-Wienberg equilibrium and linkage disequilibrium for multiple loci. The method of determining the probability of random sire exclusion uses observed genotype frequencies instead of allele frequencies. Independently, the markers used have a probability of between 0.72 and 0.62 of identifying a parentage error, while used together the five markers give, on average across breeds, a probability of 0.99 of excluding an incorrect sire.