Biomedical subjects

K L Yoon

Publications and source records attributed to K L Yoon.

4 recordsLinked to original sources

PubMed1994

Studies on the membrane topology of the (Na,K)-ATPase.

The topology of the alpha 1 and beta 1 subunits of the rat (Na,K)-ATPase has been studied by insertion of epitope(s): at the NH2 terminus and COOH terminus and between Glu-117 and Glu-118, Lys-828 and Arg-829, Gln-900 and Trp-901, and Val-939 and Phe-940 of the alpha subunit; and at the NH2 terminus and COOH terminus and between Glu-228 and Tyr-229 of the beta subunit. The epitope-tagged alpha 1 constructs were expressed in HeLa cells to select for stable cell lines expressing a functional (Na,K)-ATPase. The epitope-tagged beta constructs were transiently expressed in Cos-7 cells. The membrane arrangement of the epitopes was revealed by indirect immunofluorescence with cells expressing the (Na,K)-ATPase chains. The results indicate that the alpha subunit has 4 transmembrane segments in the COOH-terminal membrane-bound domain between residues 760 and 938, and that both the NH2 terminus and the COOH terminus are in the cytosol; it was not determined whether there are more transmembrane segments between residue 938 and the COOH terminus. The beta subunit has only one transmembrane-spanning region with the NH2 terminus in the cytosol and the COOH terminus on the extracytoplasmic surface of the plasma membrane.

Amino Acid Sequence↗

PubMed1993

Mitochondrial disorder associated with newborn cardiopulmonary arrest.

A female infant who died 2.5 d after birth with hypoglycemia, lactic acidosis, and sudden multisystem failure was studied. Biochemical studies showed complex III and IV deficiency in liver, kidney, and muscle, with muscle most severely affected. Southern blot analysis of the patient's mitochondrial DNA did not reveal any deletions. Denaturing gradient gel analysis, which detects single base changes by differences in melting behavior, showed an extra band that was not seen in mitochondrial DNA from the mother, the mother's identical twin sister, or an unrelated normal subject. This extra band indicated heteroplasmy for a restriction fragment containing the apocytochrome b and transfer RNA(thr) genes. Sequencing revealed an A to G mutation at nucleotide 15923, the last base of the anticodon loop of the transfer RNA(thr) gene. The mutation lengthens the anticodon stem by added pairing and reduces the anticodon loop size from 7 to 5 nucleotides, potentially compromising transfer RNA(thr) function in translation and/or in processing the polycistronic RNA transcript. The patient's mother previously had a male infant who also died at 1.5 d postnatal, and both the mother and her twin have had multiple miscarriages. Amniocentesis for a genetic screen was performed on the mother's twin sister during a recent pregnancy; some of the cultured cells were made available for this study. The mutation was not found in the amniocytes or in umbilical cord blood obtained at birth; the baby was normal at birth and remains healthy. It is concluded that the mutation at nucleotide 15923 was most likely the cause of the fatal disease in the index case.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1991

Denaturing gradient gel method for mapping single base changes in human mitochondrial DNA.

A denaturing gradient gel electrophoresis (DGGE) method is described that detects even single base pair changes in mitochondrial DNA (mtDNA). In this method, restriction fragments of mtDNA are electrophoresed in a urea/formamide gradient gel at 60 degrees C. Migration distance of each mtDNA fragment in the gel depends on melting behavior which reflects base composition. Fragments are located by Southern blotting with specific mtDNA probes. With just four carefully chosen restriction enzymes and as little as 50-100 ng of mtDNA, the method covers almost the entire human mitochondrial genome. To demonstrate the method, human mtDNA was analyzed. In six normal individuals, DGGE revealed melting behavior polymorphisms (MBPs) in mtDNA fragments that were not detected by restriction fragment length polymorphism (RFLP) analysis in agarose gels. Another individual, shown to have a melting behavior polymorphism in the cytochrome b coding region, was studied in detail. By mapping, the mutation was deduced to lie between nt 14905 and 15370. The affected fragment was amplified by PCR and sequenced. Specific base changes were identified in the region predicted by the gel result. This method will be especially useful as a diagnostic tool in mitochondrial disease for rapid localization of mtDNA mutations to specific regions of the genome, but DGGE also could complement RFLP analysis as a more sensitive method to follow maternal lineage in human and animal populations in a variety of research fields.

Base Sequence↗

PubMed1991

Mitochondrial tRNA(thr) mutation in fatal infantile respiratory enzyme deficiency.

The mitochondrial DNA (mtDNA) of two unrelated infants with lethal respiratory chain defects was studied using denaturing gradient gel analysis. This analysis revealed melting behavior differences suggesting a point mutation(s) in a restriction fragment containing the apocytochrome b and tRNA(thr) genes. Sequencing revealed that patient 1 had an A to G mutation at nt 15924 which is the last base pair of the anticodon stem adjacent to the anticodon loop of tRNA(thr). Patient 2 had an A to G mutation at nt 15923 which is the last base of the anticodon loop. The results suggest that mtDNA mutations affecting the anticodon loop structure of tRNA(thr) cause mitochondrial disease that is fatal in infancy.

Anticodon↗