Ligand binding and stabilization of malate- and lactate dehydrogenase

Binding of coenzymes, coenzyme fragments and phenolate ligands to malate- and lactate dehydrogenase was studied. From linear competition in titration experiments, the coenzyme binding site was concluded to bind all the ligands employed. The analogy between the phenolate ligands and tetraiodofluorescein which is known to bind at the adenosine binding site suggests binding of phenolates at this site. Coenzymes and coenzyme fragments retard the irreversible thermal inactivation of the enzymes. The retardation effect decreases in the order NADH greater than NAD greater than ADPR greater than or equal to AMP for both enzymes. Phenolate ligands binding to the adenosine pocket do not stabilize the enzymes. The stabilization is concluded to originate from the interaction of coenzyme phosphate and nicotinamide with the enzymes. The interactions with the adenosine moiety and with the second ribose seem to be ineffective in retardation of thermal denaturation.     

Isolation of a cAMP receptor protein from yeast mitochondria (Mr 45000) and comparison with mitochondrial RNA polymerase (Mr 45000)

We have isolated a cAMP-binding protein from highly purified yeast mitochondria by affinity chromatography. It is a lipophilic protein of molecular mass 45 000 Da, which is tightly membrane-bound and localized on the outer surface of the inner membrane. It can be solubilized in active form under mild conditions. The cAMP receptor resembles mitochondrial RNA polymerase prepared as described by Levens et al. [(1981) J. Biol. Chem. 256, 1474] in a surprisingly large number of properties including molecular mass. Comparison of the two proteins revealed that the polypeptide previously considered as RNA polymerase is, in fact, a mitochondrial cAMP receptor protein.     

The complete amino-acid sequence of the proteinase inhibitor B from the root of the arrowhead (Sagittaria sagittifolia L.)

After reduction and alkylation of the disulfide bonds of the proteinase inhibitor B from the root of the arrowhead (Sagittaria sagittifolia L.) followed by CNBr cleavage three peptide fragments with 68, 62 and 11 amino-acid residues could be separated on DEAE-Sepharose CL-6B. The peptides or the inhibitor itself were further specifically cleaved either by trypsin or by the mixture of (CH3)2SO/HCl/HBr at the arginyl- and the tryptophyl-peptide bond, respectively. The complete amino-acid sequences of the peptides were determined by manual solid phase DABITC/PITC double coupling micro-method and the primary structure of the arrowhead inhibitor B consisting of 141 amino-acid residues was then elucidated. Twenty pairs of amino-acid residues are repeated in the molecule of this inhibitor, three of these pairs even occur three times. The possible locations of the reactive sites are discussed. On the basis of sequence comparisons between this inhibitor and all other serine proteinase inhibitors the arrowhead inhibitor may belong to a new family.     

Post-synthetic modification of proteins

Process of postsynthetic modifications of proteins in norm are considered. Two basic groups of modification processes are singled out: 1) processes which promote appearance of derivatives for 20 basic amino acids, i.e. change in the primary structure; 2) processes which are not associated with appearance of new amino acids but are responsible mainly for the changes in the polypeptide chain conformation and size. Modification processes of amino acid variations by means of methylation, acetylation, acylation, phosphorylation, ADP-ribosylation, glycosylation, amidation, hydroxylation and metal addition are described as referred to the first group. Proteolysis reactions are characterized in detail. Their significance for formation of biologically active peptides is considered. A notion "one gene--one protein" is thought to be incompetent because formation of a number of proteins necessitates participation of tens and hundreds of genes, coding enzymes of postsynthetic modification.     

Localized mutagenesis of the tetracycline gene in the plasmid pBR322 induced by sodium bisulfite in vitro

The technique of localized in vitro mutagenesis in the cohesive ends of plasmid pBR322 DNA has been elaborated (separately for BamHI and HindIII sites). Plasmid DNA digested by restriction endonucleases has been treated with sodium bisulphite deaminating cytosine to form uracil in single stranded DNA (cohesive ends of the plasmid). The mutagenized plasmid DNA, free of mutagen, has been treated with bacteriophage T4 ligase. E. coli C600 cells were subsequently transformed by the ligated DNA preparation. The clones having tetracycline gene mutagenized represented 4.0-11.1% and 1.2-3.1% among HindIII and BamHI mutants, respectively, selected as TcR----TcS transformants. Selection of mutagenized DNA by the second endonuclease restriction has increased the mutant yields up to 55.6-78.0% and 10.0-75.4%, respectively. The yield of TcS mutations in the control DNA treated at all stages of experiment, except for mutagen treatment, has reached 0.06% and 0.2%, respectively.     

Analysis of ribonucleoproteins of influenza virus containing genomic and complementary RNA

The density and sedimentation characteristics of ribonucleoproteins (RNP) containing genomic RNA from influenza virus and RNA complementary have been studied. Radioactive RNA from infected cells has been used for analysis. RNA classes of interest were isolated by reannealing with abundant nonradioactive genomic and complementary RNA and separation of resulting duplexes in electrophoresis. The RNP containing antigenomic virus-specific RNA are practically identical to "genomic" RNP for their sedimentation and density characteristics. The "plus" RNP is characterized by the stoichiometric mode of RNA protein interaction.     

大熊猫(Ailuropoda melanolenca)显带染色体的研究

大熊猫系我国特产的世界珍稀动物,素有“活化石”和“国宝”之称。限于材料来源,虽有核型的少数报道（邓承宗等,1980;陈文元等,1984;Newnham et al.,1966）,但研究尚不够深入。1980年,Wurster-Hill和Bush首先报道了大熊猫（）的显带核型,并与杂交熊等比较,探讨了大熊猫的分类地位。本文对四只大熊猫的G带、C带核型和Ag-NORs作了分析,绘制了G带核型模式图,并提出了某些商榷的意见。     

猕猴(Macaca mulatta)主动脉弓的分支类型

随着心血管系统研究的进展和猿猴在医学中的广泛应用,猴主动脉弓分支的情况引起人们的重视。虽然张胜泉等（1974）对猕猴的心脏冠状动脉的解剖学作过调查,但有关主动脉弓分支的资料很少。为此,我们进行了本题研究,以供参考。     

The effect of corrective surgery on energy expenditure during ambulation in children with cerebral palsy

Mechanical efficiency, heart rate, blood lactate, and some other variables were studied in six children with cerebral palsy who walked on a treadmill before and after corrective surgery. During each test, conducted at each child's naturally selected speed, two situations were studied: steady state level walking for 9 min, and then walking at an increasing inclination up to 20% for another 10 min. During the test the subjects were allowed to hold on to a handrail to eliminate the risk of falling off the treadmill. The corrective surgery resulted in a 5% reduction in oxygen consumption per kg body mass during level walking. The subjects' levels of physical fitness, as estimated from oxygen pulse, however, were unchanged. These results are indicative of a biomechanical improvement due to the corrective surgery. While walking at a 20% inclination the subjects off loaded themselves to different degrees on the handrail which influenced the results. Their feeling of exhaustion at this load was probably due to local factors, since heart rate was well below maximal values, and blood lactate, respiratory exchange ratio and ventilatory equivalent also indicated that they were below their anaerobic thresholds (50-60% of maximal oxygen uptake).