Inactivation of L-lysine decarboxylase by L-lysine bromomethyl ketone

The mitogenome portrait of Umbria in Central Italy as depicted by contemporary inhabitants and pre-Roman remains

Umbria is located in Central Italy and took the name from its ancient inhabitants, the Umbri, whose origins are still debated. Here, we investigated the mitochondrial DNA (mtDNA) variation of 545 present-day Umbrians (with 198 entire mitogenomes) and 28 pre-Roman individuals (obtaining 19 ancient mtDNAs) excavated from the necropolis of Plestia. We found a rather homogeneous distribution of western Eurasian lineages across the region, with few notable exceptions. Contemporary inhabitants of the eastern part, delimited by the Tiber River and the Apennine Mountains, manifest a peculiar mitochondrial proximity to central-eastern Europeans, mainly due to haplogroups U4 and U5a, and an overrepresentation of J (30%) similar to the pre-Roman remains, also excavated in East Umbria. Local genetic continuities are further attested to by six terminal branches (H1e1, J1c3, J2b1, U2e2a, U8b1b1 and K1a4a) shared between ancient and modern mitogenomes. Eventually, we identified multiple inputs from various population sources that likely shaped the mitochondrial gene pool of ancient Umbri over time, since early Neolithic, including gene flows with central-eastern Europe. This diachronic mtDNA portrait of Umbria fits well with the genome-wide population structure identified on the entire peninsula and with historical sources that list the Umbri among the most ancient Italic populations.

The spread of steppe and Iranian-related ancestry in the islands of the western Mediterranean

Steppe-pastoralist-related ancestry reached Central Europe by at least 2500 BC, whereas Iranian farmer-related ancestry was present in Aegean Europe by at least 1900 BC. However, the spread of these ancestries into the western Mediterranean, where they have contributed to many populations that live today, remains poorly understood. Here, we generated genome-wide ancient-DNA data from the Balearic Islands, Sicily and Sardinia, increasing the number of individuals with reported data from 5 to 66. The oldest individual from the Balearic Islands (~2400 BC) carried ancestry from steppe pastoralists that probably derived from west-to-east migration from Iberia, although two later Balearic individuals had less ancestry from steppe pastoralists. In Sicily, steppe pastoralist ancestry arrived by ~2200 BC, in part from Iberia; Iranian-related ancestry arrived by the mid-second millennium BC, contemporary to its previously documented spread to the Aegean; and there was large-scale population replacement after the Bronze Age. In Sardinia, nearly all ancestry derived from the island's early farmers until the first millennium BC, with the exception of an outlier from the third millennium BC, who had primarily North African ancestry and who-along with an approximately contemporary Iberian-documents widespread Africa-to-Europe gene flow in the Chalcolithic. Major immigration into Sardinia began in the first millennium BC and, at present, no more than 56-62% of Sardinian ancestry is from its first farmers. This value is lower than previous estimates, highlighting that Sardinia, similar to every other region in Europe, has been a stage for major movement and mixtures of people.

Labelling of L-isoleucine tRNA ligase from Escherichia coli with L-isoleucyl-bromomethyl ketone

L-Isoleucine: tRNA ligase from Escherichia coli could be irreversibly inactivated by L-isoleucyl-bromomethyl ketone but not by L-isoleucyl-chromethyl ketone. The inactivation rate exhibited a saturation concentration dependence typical for an affinity reagent. L-Isoleucine provided 100% protection against inactivation at saturating concentration, whereas ATP, AMP, and pyrophosphate offered partial protection and tRNAIle, no protection. The ligase was labelled in preparative scale with L-[14C]isoleucyl-bromethyl ketone. The molar ration of label incorporated to enzyme inactivated was close to unity. The protein was subsequently subjected to tryptic digestion and the radioactive peptide isolated and identified. The labelled amino acid proved to be the same cysteine previously reported as being labelled with N-[14C]ethylmaleimide [Kula, M.-R. (1974) FEBS Lett. 46, 130-133].