The integrity of healthy mitochondria is supposed to depend largely on proper mitochondrial protein biosynthesis. Mitochondrial ribosomal proteins (MRPs) are directly involved in this process. To identify mammalian mitochondrial ribosomal proteins and their corresponding genes, we purified mature rat MRPs and determined 12 different N-terminal amino acid sequences. Using this peptide information, data banks were screened for corresponding DNA sequences to identify the genes or to establish consensus cDNAs and to characterize the deduced MRP open reading frames. Eight different groups of corresponding mammalian MRPs constituted from human, mouse, and rat origin were identified. Five of them show significant sequence similarities to bacterial and/or yeast mitochondrial ribosomal proteins. However, MRPs are much less conserved in respect to the amino acid sequence among species than cytoplasmic ribosomal proteins of eukaryotes and bacteria.Intact mitochondrial protein biosynthesis has been shown to be indispensable for the maintenance of mitochondrial DNA in yeast (1). Nearly all of the mitochondrial ribosomal proteins (MRPs) 1 investigated so far are essential for proper mt protein synthesis (2). Knock-out mutants of yeast MRP genes lose their respiratory capacity and change to Ϫ or o mt genetic status by successive losses of mt DNA (1). In higher eukaryotes, the knowledge about comparable functions of MRPs is only rudimentary, since only a few MRPs have been characterized on the molecular level. The protein composition of mammalian mt ribosomes has been studied extensively (3-5). Some properties of mt ribosomes such as structure (6), binding of nucleotides and RNA (7-11), and interaction with different factors have been studied (12)(13)(14). However, only 3 of the approximately 80 -100 different human MRPs have been described at the molecular level so far. MRL3, which is the EcoL3 counterpart in human mt ribosomes, was identified as an overexpressed r-protein in Mahlavu hepatomic cells (15). Later, it was postulated to be a true MRP by virtue of its sequence similarity to the corresponding yeast MRP YmL9 (16). MRPL12 was identified as a delayed-early response gene similar in sequence to the Escherichia coli L7/L12 r-protein (17). The metazoan mitochondrial counterpart of EcoS12 has been characterized in Drosophila, human, and mouse (18,19). In Drosophila a mutation of mt S12 causes abnormal behavior. This is the first case reported so far of affection of the status of an animal by an MRP mutation (18). Diseases affecting mitochondria are known in humans, and are caused by nuclear mutations responsible for the loss of mt DNA as a secondary effect by a so far unknown mechanism (20, 21). Mutations of MRPs are good candidates affecting mt genetic and/or physiological status. To characterize mammalian MRPs and to compare their biochemical properties with that of their (essential) counterparts, e.g. of yeast, we identified several mammalian MRPs and their corresponding gene sequences. We used N-terminal sequence inform...

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Upper Cretaceous mudstones are the most important source rocks in the Termit Basin, SE Niger. For this study, 184 mudstone samples from the Santonian–Campanian Yogou Formation and the underlying Cenomanian–Coniacian Donga Formation from eight wells were analyzed on the basis of palaeontological, petrographical and geochemical data, the latter including the results of Rock‐Eval, biomarker and stable isotope analyses. Samples from the upper member of the Yogou Formation contain marine algae and ostracods together with freshwater algae (Pediastrum) and arenaceous foraminifera, indicating a shallow‐marine to paralic depositional environment with fresh‐ to brackish waters. Terrestrial pollen and spores are common and of high diversity, suggesting proximity to land. Samples from the lower member contain marine algae and ostracods and arenaceous foraminifera but without freshwater algae, indicating shallow‐marine and brackish‐water settings with less freshwater influence.The wide range of gammacerane index values, gammacerane/C30 hopane (0.07–0.5) and Pr/Ph ratios (0.63–4.68) in samples from the upper member of the Yogou Formation suggest a low to moderately saline environment with oxic to anoxic conditions. In samples from the lower member, the narrower range of the gammacerane index (0.23∼0.35) and Pr/Ph ratios (0.76–1.36) probably indicate a moderately saline environment with suboxic to relatively anoxic conditions.Petrographic analyses of the Yogou Formation samples show that organic matter is dominated by terrestrial higher plant material with vitrinite, inertinite and specific liptinites (sporinite, cutinite and resinite). Extracts are characterized by a dominance of C29 steranes over C27 and C28 homologues. Results of pyrolysis and elemental analyses indicate that the organic matter is composed mainly of Type II kerogen grading to mixed Type II‐III and Type III material with poor to excellent petroleum potential. Mudstones from the upper member of the Yogou Formation have higher petroleum generation potential than those from the lower member. Mudstones in the Donga Formation are dominated by Type III organic matter with poor to fair petroleum generation potential.Geochemical parameters indicate that in terms of thermal maturity the Yogou Formations has reached or surpassed the early phase of oil generation. Samples have Tmax values and 20S/(20S+20R) C29 sterane ratios greater than 435°C and 0.35, respectively. 22S/(22S+22R) ratios of C31 homohopanes range from 0.50 to 0.54.The results of this study will help to provide a better understanding of the hydrocarbon potential of Upper Cretaceous marine source rocks in the Termit Basin and also in coeval intracontinental rift basins such as the Tenere Basin (Niger), Bornu Basin (Nigeria) and Benue Trough (Nigeria).

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