MDH1 Research Articles

Clinal variation and selection of MDH allozymes in honey bee populations.

Latitudinal clines of malate dehydrogenase-1 (MDH-1) allozymes occur within honey bee populations on three continents: Europe, North America and South America. The North and South American populations are introduced and demonstrate that Mdh allelic clines were established within the last 150 years. The frequency of the 'medium' electrophoretic allele increases in frequency with increasing latitude while the 'fast' allele decreases with latitude on all the three continents. The clines are best explained by the average daily high temperature for July on all continents. These parallel clines provide evidence for selection on Mdh alleles in honey bees.

Glucose-induced degradation of the MDH2 isozyme of malate dehydrogenase in yeast.

MDH2, the nonmitochondrial isozyme of malate dehydrogenase in Saccharomyces cerevisiae, was determined to be a target of glucose-induced proteolytic degradation. Shifting a yeast culture growing with acetate to medium containing glucose as a carbon source resulted in a 25-fold increase in turnover of MDH2. A truncated form of MDH2 lacking amino acid residues 1-12 was constructed by mutagenesis of the MDH2 gene and expressed in a haploid yeast strain containing a deletion disruption of the corresponding chromosomal gene. Measurements of malate dehydrogenase specific activity and determination of growth rates with diagnostic carbon sources indicated that the truncated form of MDH2 was expressed at authentic MDH2 levels and was fully active. However, the truncated enzyme proved to be less susceptible to glucose-induced proteolysis, exhibiting a 3.75-fold reduction in turnover rate following a shift to glucose medium. Rates of loss of activity for other cellular enzymes known to be subject to glucose inactivation were similarly reduced. An extended lag in attaining wild type rates of growth on glucose measured for strains expressing the truncated MDH2 enzyme represents the first evidence of a selective advantage for the phenomenon of glucose-induced proteolysis in yeast.

Isolation, nucleotide sequence analysis, and disruption of the MDH2 gene from Saccharomyces cerevisiae: evidence for three isozymes of yeast malate dehydrogenase.

The major nonmitochondrial isozyme of malate dehydrogenase (MDH2) in Saccharomyces cerevisiae cells grown with acetate as a carbon source was purified and shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to have a subunit molecular weight of approximately 42,000. Enzyme assays and an antiserum prepared against the purified protein were used to screen a collection of acetate-nonutilizing (acetate-) yeast mutants, resulting in identification of mutants in one complementation group that lack active or immunoreactive MDH2. Transformation and complementation of the acetate- growth phenotype was used to isolate a plasmid carrying the MDH2 gene from a yeast genomic DNA library. The amino acid sequence derived from complete nucleotide sequence analysis of the isolated gene was found to be extremely similar (49% residue identity) to that of yeast mitochondrial malate dehydrogenase (molecular weight, 33,500) despite the difference in sizes of the two proteins. Disruption of the MDH2 gene in a haploid yeast strain produced a mutant unable to grow on minimal medium with acetate or ethanol as a carbon source. Disruption of the MDH2 gene in a haploid strain also containing a disruption in the chromosomal MDH1 gene encoding the mitochondrial isozyme produced a strain unable to grow with acetate but capable of growth on rich medium with glycerol as a carbon source. The detection of residual malate dehydrogenase activity in the latter strain confirmed the existence of at least three isozymes in yeast cells.

Isolation, Nucleotide Sequence Analysis, and Disruption of the MDH2 Gene from Saccharomyces cerevisiae: Evidence for Three Isozymes of Yeast Malate Dehydrogenase

The major nonmitochondrial isozyme of malate dehydrogenase (MDH2) in Saccharomyces cerevisiae cells grown with acetate as a carbon source was purified and shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to have a subunit molecular weight of approximately 42,000. Enzyme assays and an antiserum prepared against the purified protein were used to screen a collection of acetate-nonutilizing (acetate-) yeast mutants, resulting in identification of mutants in one complementation group that lack active or immunoreactive MDH2. Transformation and complementation of the acetate- growth phenotype was used to isolate a plasmid carrying the MDH2 gene from a yeast genomic DNA library. The amino acid sequence derived from complete nucleotide sequence analysis of the isolated gene was found to be extremely similar (49% residue identity) to that of yeast mitochondrial malate dehydrogenase (molecular weight, 33,500) despite the difference in sizes of the two proteins. Disruption of the MDH2 gene in a haploid yeast strain produced a mutant unable to grow on minimal medium with acetate or ethanol as a carbon source. Disruption of the MDH2 gene in a haploid strain also containing a disruption in the chromosomal MDH1 gene encoding the mitochondrial isozyme produced a strain unable to grow with acetate but capable of growth on rich medium with glycerol as a carbon source. The detection of residual malate dehydrogenase activity in the latter strain confirmed the existence of at least three isozymes in yeast cells.

Isozyme variation and the reproductive biology of Hydrocharis morsus-ranae L. (Hydrocharitaceae)

Electro-phoretically detectable isozyme variation was studied for 17 enzyme systems in several N American populations of the introduced aquatic plant Hydrocharis morsus-ranae and in two European populations. Twenty-nine loci were inferred from progeny, adult and turion enzyme banding patterns with 28 of these loci homozygous in all individuals studied. Malate dehydrogenase-1 (MDH-1) was the only locus which could be interpreted as multi-allelic and heterozygous. Twenty-seven of 76 seedlings assayed showed an age specific expression for an alcohol dehydrogenase locus (ADH-2) never seen in adults or turions. Since all adults sampled were phenotypically identical at all loci assayed, it is possible that only one isozyme genotype of this species is present in N America. European turion data further indicated that the populations studied were identical to N American plants sampled at all loci except EST. Therefore, although H. morsus-ranae is dioecious, outcrossing appears to involve substantial inbreeding. Connections between extensive inbreeding and the failure of effective sexual reproduction are considered.

Linkage Group V of Platyfishes and Swordtails of the Genus <italic>Xiphophorus</italic> (Poeciliidae): Linkage of Loci for Malate Oehydrogenase-2 and Esterase-1 and Esterase-4 With a Gene ContrOlling the Severity of Hybrid Melanomas<xref ref-type="fn" rid="FN2">2</xref><xref ref-type="fn" rid="FN3">3</xref>

Electrophoretic variations ascribable to three enzyme loci coding for esterase-1 and -4 (ES1 and ES4) and a malate dehydrogenase-2 isozyme (MDH2) were studied in interspecific backcrosses of fishes of the genus Xiphophorus (Poeciliidae). Normal segregation was demonstrated for all three loci. Linkage analyses indicated a gene order of ES1-6%-ES4-33%-MDH2. This group [designated linkage group (LG) V] was shown to assort independently from the 11 loci comprising LG's I-IV and from 18 other informative markers, with the limits of the data. A factor controlling the extent of development of inherited melanomas was demonstrated to be associated only with LG V loci, implying predominant control by a single gene, which probably determines the completeness of differentiation of macromelanophores in hybrids. Possible explanations for variability in the apparent chromosomal position of the melanoma severity gene, as assessed by estimates of recombination with the LG V enzyme loci, are discussed.

An assessment of "hidden" heterogeneity within electromorphs at three enzyme loci in deer mice.

Allelic heterogeneity within protein electromorphs at three loci was examined in populations of deer mice (Peromyscus maniculatus) collected from five localities across North America. We used a variety of electrophoretic techniques (including several starch and acrylamide conditions, gel-sieving, and isoelectric focusing) plus heat denaturation. Of particular interest was the supernatant glutamate oxalate transaminase system (GOT-1; aspartate aminotransferase-1 of some authors), which under standard electrophoretic conditions had been shown to exhibit basically a two-allele polymorphism throughout the range of maniculatus. The use of all of the above techniques failed to uncover any additional variation for GOT-1 in these populations. Similarly, no new scorable variation was resolved at the essentially monomorphic malate dehydrogenase-1 locus by additional conditions of electrophoresis. In marked contrast to the results for the above two enzymes, the use of multiple conditions of electrophoresis resolved the 8 standard-condition electromorphs of esterase-1 into a total of 23 variants showing strong geographic differentiation in frequency. These 23 electromorphs were further divided into a total of 35 variants by thermal stability studies. However, the allelic nature of all of the thermal stability esterase variants remains to be documented. The results of this study, taken together with the remarkable geographic heterogeneity for this species in ecology, morphology, karyotype and mitochondrial DNA sequence, suggest that some form of balancing selection may be acting to maintain the GOT-1 polymorphism.

Methionyl-tRNA synthetase shows the nucleotide binding fold observed in dehydrogenases.

A striking common structural feature has emerged from the comparison of the X-ray crystallographic studies of several dehydrogenases. In lactate dehydrogenase1, soluble malate dehydrogenase2, alcohol dehydrogenase3 and glyceraldehyde-3-phosphate dehydrogenase4 similar foldings have been described in the region which binds the coenzyme NAD, whereas no significant similarities were observed in the chemical sequences. The occurrence of a characteristic ‘nucleotide binding fold’ (the so-called Rossmann fold) has also been observed in horse muscle phosphoglycerate kinase5, in phosphorylase6,7 and, with some topological deviations, in other kinases8–11 as well as in the flavin-binding domain of flavodoxin12. If one assumes that these structural homologies are the result of a divergent evolutionary process, it is then tempting to predict a similar pattern of structure–function relationship in other nucleotide-binding proteins, in particular in aminoacyl-tRNA synthetases. We show here that methionyl-tRNA synthetase does show the same nucleotide binding fold.

Regional localization of the human genes for malate dehydrogenase-1 and isocitrate dehydrogenase-1 on chromosome 2 by interspecific hybridization using human cells with the balanced reciprocal translocation t(1;2) (q32;q13).

Regional localization of the human genes for malate dehydrogenase-1 and isocitrate dehydrogenase-1 on chromosome 2 by interspecific hybridization using human cells with the balanced reciprocal translocation t(1;2) (q32;q13).

Nonmetric Analysis of Genetic Relationships among Inbred Strains of Mice

Guttman, Ruth and Louis Guttman (Department of Psychology, The Hebrew University of Jerusalem, Israel, and The Israel Institute of Applied Social Research, Jerusalem) 1974. Nonmetric analysis of relationships among inbred strains of mice. Syst. Zool. 23: 355-362.-A multidimensional scalogram analysis, MSA-I, shows that 27 inbred mouse strains, classified by thirteen loci, can be represented as points in a two-dimensional space. Five of the loci provide a rectangular coordinate system for partitioning of the space, three a polar, while the remaining ones make little further systematic contribution. The systematic partitionings may suggest theories of the origin of the strains' similarities and differences. [Nonmetric analysis; relationships; inbred mice.] In comparing subgroups of populations of common origin, several different methods have been developed that attempt to estimate degrees of relatedness or of genetic between these populations. Nei (1972) has critically reviewed a number of such methods and proposed a measure of distance based on the identity of genes in local populations within a species. A conceptually more satisfying procedure is that of Taylor (1972) who has used the distribution of alleles at 16 polymorphic loci in 27 inbred strains of mice to produce a two-dimensional plot of these strains on the basis of an eigenvector analysis of their similarity matrix. This plot gives a graphic picture of the relative similarity of the strains based on all the information available, and shows whether a strain is relatively common or distinctive on the basis of the average number of shared alleles with the other 26 strains. The eigenvector method of analysis has, however, at least four limitations, some of them pointed out by Taylor himself. One limitation is the need to calculate similarity coefficients. This involves an arbitrary decision, Taylor's being simply to count the number of shared alleles for each pair of strains. A second limitation is the use of linear (vector) methods for basically qualitative (dichotomous) data. A third is the lack of a clear stopping rule as to how many eigenvectors to use. Finally, the most important limitation may be the loss of information about the individual loci by focusing on the mouse strains alone as points in the derived space. The present paper presents a reanalysis of Taylor's data which avoids these four limitations. The reanalysis plots the 27 strains as points in a two-dimensional space that is not unlike Taylor's approximation, but in which the role of each locus is made explicit for partitioning the space. No similarity coefficients are needed. The analysis is based directly on the observed distributions of alleles over the strains, as given in Taylor's Table 1 (1972, p. 83). The analysis is nonmetric rather than vectorial, as is appropriate for the qualitative nature of the data involved. Of the sixteen polymorphic loci given in Taylor's Table 1, thirteen have been used in this analysis. Each of the three that were omitted (Es-2, Pgm-2, and Ldr-1) had identical alleles in all but one or two strains. The data used in this analysis are given in Table 1. The loci are Es-1:esterase-1; Es-3:esterase-3; Mod-l:NADP malate dehydrogenase-1; Id-i :isocitrate dehydrogenase-1; Gpd-i:autosomal glucose 6-phosphate dehydrogenase-1; Gpi-i glucose phosphate isomerase-i; Pgm-l :phosphoglucomutase-i; Hbb:hemoglobin beta chain; Dip-l:dipeptidase-i; H2:the histocompatibility locus; Hc:serum complement; rd:retinal degeneration; and In:7-12 dimethylbenzanthracene inflammatory response.