| Summary: | 16 pages, 7 figures.-- PMID: 2466240 [PubMed].-- PMCID: PMC331823. An 11 S ribonucleoprotein particle was isolated from maize endosperm and shown to be functionally and structurally equivalent to the mammalian signal recognition particle. However, unlike animal cells which apparently contain a single 7 SL RNA species, maize endosperm contains a heterogeneous population of 7 SL RNA. To investigate this diversity, we have cloned and sequenced a number of the maize endosperm 7 SL RNAs isolated from functionally active SRP preparations. Some maize 7 SL RNAs are strikingly similar, differing by single base changes or short deletions; surprisingly, others share less than 70 percent sequence homology. Despite differences in primary sequence, nearly identical secondary structures can be suggested for all maize 7 SL RNAs, consistent with a proposed functional role in protein translocation for each of these RNAs. The amount of new available sequence data enabled us to define two conserved regions of presumed functional importance: A conserved sequence -G-N-A-R- in the center of a variable region which forms a well defined stem-loop and possibly is involved in an interaction with the 19 kDa protein of the SRP. Secondly, three short nucleotide stretches located in the central domain of 7 SL RNA may form part of a dynamic RNA-switch structure. It was supported by a grant of the Spanish CAICRT and by EMBO. We like to thank Bernhard Dobberstein for support, Christopher Marshallsay for technical assistance, Siegfried Prehn and Abu Sami for valuable comments and enjoyable discussions and Ibrahim Ibrahimi and Michael Fordis for critical reading of the manuscript. N.C. thanks the tenure of a Ph.D. scholarship from the Ministerio de Educacion J Ciencia of Spain. Peer reviewed
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