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[摘要]：The formation and breaking of hydrogen bonds between nucleic acid bases are dependent on temperature. The high G + C content of organisms was surmised to be an adaptation for high temperature survival because of the thermal stability of G:C pairs. However, a survey of genomic GC% and optimum growth temperature (OGT) of several prokaryotes revoked any direct relation between them. Significantly high purine (R=A or G) content in mRNAs is also seen as a selective response for survival among thermophiles. Nevertheless, the biological relevance of thermophiles loading their unstable mRNAs with excess purines (purine-loading or R-loading) is not persuasive. Here, we analysed the mRNA sequences from the genomes of 168 prokaryotes (as obtained from NCBI Genome database) with their OGTs ranging from -5 degrees C to 100 degrees C to verify the relation between R-loading and OCT. Our analysis fails to demonstrate any correlation between R-loading of the mRNA pool and OCT of a prokaryote. The percentage of purine-loaded mRNAs in prokaryotes is found to be in a rough negative correlation with the genomic GC% (r(2) = 0.655, slope = -1.478, P<000.1). We conclude that genomic GC% and bias against certain combinations of nucleotides drive the mRNA-synonymous (sense) strands of DNA towards variations in R-loading. (C) 2012 Elsevier B.V. All rights reserved. |
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