We review the relationship between various types of mitochondrial DNA mutations and the prevalence as well as the pathobiochemical and clinical features of mitochondrial diabetes mellitus. An A to G transversion mutation in the tRNA(Leu(UUR)) gene is associated with diabetes in about 1.5% of the diabetic population in different countries and races. Phenotypically this type of mitochondrial diabetes is combined with deafness in more than 60% and is clinically distinguishable with respect to several characteristics from the two idiopathic forms of diabetes. The underlying pathomechanism is probably a delayed insulin secretion due to an impaired mitochondrial ATP production in consequence of the mtDNA defect.

The primary structure of the a subunit of elongation factor 1 (EF-la) from human MOLT 4 cells was determined by cDNA sequencing. The data show that the conservation of the amino acid sequence is more than 80% when compared with yeast and Artemia EF-la. An inventory of amino acid sequences around the guaninenucleotide-binding site in elongation factor Tu from Escherichia coli and homologous amino acid sequences in G proteins, initiation and elongation factors and proteins from the RAS family shows two regions containing conserved sequence elements.Region I has the sequence apolar-Xaa-Xaa-Xaa-Gly-Xaa-Xaa-Yaa-Xaa-Gly-Lys-Thr(Ser)-Xaa-Xaa-XaaXaa-X-apolar. Except for RAS proteins, Yaa is always an acidic amino acid residue. Region I1 is characterized by the invariant sequence apolar-apolar-Xaa-Xaa-Asn-Lys-Xaa-Asp. In order to facilitate sequence comparison we have used a graphic display, which is based on the hydrophilicity values of individual amino acids in a sequence.The a subunit of elongation factor 1 (EF-la) is involved in binding of aminoacyl-tRNAs to 80s ribosomes. During this process GTP is hydrolyzed into GDP. In order to perform this function, EF-la has domains that bind guanine nucleotides, 80 S ribosomes and aminoacyl-tRNAs. In addition EF-la interacts with EF-lP to exchange bound GDP for GTP [I]. EF-la shares this property of exchange with G proteins, a class of proteins that is involved in modulating adenyl cyclase activity during signal transduction by hormones [2].Comparison of the amino acid sequences of different EFlas and other proteins having similar or related functions may help to obtain insight in the structural elements of EF-la that are involved in the many functions of this protein.Recently we have reported on the amino acid sequence of EF-la from the brine shrimp Artemia [3]. Also the sequence of EF-la from yeast has been published recently [4-61.Here we present the cDNA-derived amino acid sequence of human EF-la, which is another example of a guaninenucleotide-binding protein. Conserved sequence elements in several classes of guanine-nucleotide-binding proteins have been reported and discussed before [7 -141. We have extended the sequence comparison of regions supposed to be important for guanine nucleotide binding using a graphic display based on the hydrophilicity values of consecutive amino acids in such a sequence element.The data show striking similarities in the hydrophilicity pattern of two distinct regions in initiation and elongation factors, G proteins and proteins from the RAS family.Correspondence to W. Moller, Sylvius Laboratoria, P.O. Box 9503, NL-2300-RA Leiden, The Netherlands Ahhreviations. EF-1, elongation factor 1 ; cDNA, complementary DNA; SDS, sodium dodecyl sulphate.Enzymes (IUB Recommendations, 1984). DNA polymerase 1 (EC 2.7.7.7); polynucleotide kinase (EC 2.7.1.78); restriction enzymes: AvaI, Fnu4H1, Hinfl, MspI, Pvu2, RsaI, San3A1, Tag1 (EC 3.1.21.4). MATERIALS AND METHODS Isolation and characlerization of EF-a cDNA clonesA human cDNA bank in pBR322 was construct...

cDNA complementary to mRNA coding for the elongation factor EF‐1β has been cloned. A γgt 11 cDNA library has been screened with an antiserum against EF‐1β which exchanges GDP bound to EF‐1α with exogenous GTP during protein synthesis. The derived amino acid sequence corresponds to 208 amino acids including the N‐terminal methionine which is absent in the mature protein. About sixty percent of the protein was sequenced by direct protein sequence analysis. Comparison of Artemis salina EF‐1β with Escherichia coli EF‐Ts shows no evident homology.

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The localization of the protein L7/L12 relative to protein L10 in the Escherichia coli ribosome was studied by fluorescence energy transfer. N-[7-(Dimethylamino)-4-methylcoumarinyl]maleimide, coupled to Cys-70 of L10, served as a donor for fluorescein which was attached to Lys-51 or to the N terminus of L7/L12. The binding of the fluorescein-L7/L12 dimers to a strong and a weak binding site in 50S ribosomes could be distinguished. Therefore, it was possible to measure the distances between Cys-70 of L10 and Lys-51 and the N terminus of each L7/L12 dimer. For L7/L12 in the strong binding site, these two distances are both about 43 A, and for L7/L12 in the weak binding site, both are about 56 A.