Nucleic Acids Research, 1989, Vol. 17, No. 4 1573-1588
© 1989
MOLECULAR BIOLOGY |
Diversity of 7 SL RNA from the signal recognition particle of maize endosperm
Department de Biologia Molecular i Agrobiologia Jordi Girona Salgado, 18-26, 08034 Barcelona, Spain 1Laboratory of Molecular Biology, National Cancer Institute Bethesda, MD 20892, USA
*To whom correspondence should be addressed
Received November 2, 1988. Accepted January 16, 1989.
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.