instruction:
Given a context passage, generate a question from the passage such that its answer is shortest continous span from the passage.
question:
Contrary to earlier beliefs, viruses are not the smallest causative agents of infectious diseases. Single-stranded RNAs as small as 246 nucleotides exist in certain higher plants and cause more than a dozen crop diseases. These RNAs have been termed viroids. Despite their extremely limited information content, viroids replicate autonomously in susceptible cells--that is, they do not require helper functions from simultaneously replicating conventional viruses. Viroids are covalently closed circular molecules with a characteristic rodlike secondary structure in which short helical regions are interrupted by internal and bulge loops. Viroids are not translated; they are replicated by a host enzyme (or enzymes) (probably RNA polymerase II) via oligomeric RNA intermediates by a rolling circle mechanism. Viroidlike satellite RNAs resemble viroids in size and molecular structure, but are found within the capsids of specific helper viruses on which they depend for their own replication. These RNAs are of great interest to molecular biology for at least two reasons: 1) they are the smallest and simplest replicating molecules known, and 2) they may represent living fossils of precellular evolution in a hypothetical RNA world.
answer:
Which are the smallest known subviral pathogens of plants?


question:
Parkinson's disease is the most common neurodegenerative movement disorder. The motor impairments of Parkinson's disease are caused by the loss of dopaminergic neurons in the substantia nigra and associated with the appearance of fibrillar aggregates of -synuclein (-syn) called Lewy bodies. Approximately 90% of -syn deposited in Lewy bodies is phosphorylated at serine 129 (Ser129). In contrast, only 4% or less of total -syn is phosphorylated at this residue in the normal brain. This suggests that the accumulation of Ser129-phosphorylated -syn leads to the formation of Lewy bodies and dopaminergic neurodegeneration in Parkinson's disease. Our laboratory and others have performed experiments using in vivo models of Parkinson's disease to elucidate the role of increased Ser129 phosphorylation in -syn neurotoxicity. However, there has been a lack of consistency among these models. In this review, we summarize the main findings regarding the relationship between Ser129 phosphorylation and -syn neurotoxicity, and examine the differences among models. We further discuss the role of Ser129 phosphorylation in -syn aggregation and the future directions to test the potential of Ser129 phosphorylation as a therapeutic target for slowing the progression of Parkinson's disease.
answer:
Which residue of alpha-synuclein was found to be phosphorylated in Lewy bodies?


question:
Selenoprotein P is a protein of considerable intrigue, due to its unusual composition and requirements for its biosynthesis. Whereas most selenoproteins contain a single selenocysteine residue, the human, bovine and rodent selenoprotein P genes encode proteins containing 10-12 selenocysteines. Selenoprotein P genes have, to date, only been reported in mammals, and the function of the protein remains elusive. Herein, we report the identification and characterization of nonmammalian selenoprotein P in the zebrafish Danio rerio. Sequencing of the cDNA revealed the presence of 17 selenocysteine codons, the highest number reported in any protein. Two histidine-rich regions present in the mammalian selenoprotein P sequences are conserved in the zebrafish protein, and two SECIS elements are present in the 3' untranslated region. Whole-mount in situ hybridization of zebrafish embryos revealed high levels of expression of selenoprotein P mRNA in fertilized eggs and in the yolk sac of developing embryos. Transient transfection of the cDNA in mammalian cells resulted in efficient expression of the full-length secreted selenoprotein. A single N-glycosylation site is predicted, and shown to be utilized. Discovery of selenoprotein P in the zebrafish opens a previously unavailable avenue for genetic investigation of the functions of this unusual protein.
answer:

Which is the human selenoprotein that contains several Se-Cys residues?