The tRNA type II V arm and type I V loop

Origin of Life

In an ancient organism, there are 5 tRNALeu and 4 tRNASer. Because there are so many anticodons, the type II V arm is read by LeuRS-IA and SerRS-IIA (the enzymes that add leucine or serine to their cognate tRNAs).

LeuRS-IA reads the type II tRNALeu V arm end loop (i.e., V6-UAG-V8; red asterisks).

SerRS-IIA reads the trajectory of the type II tRNASer V arm and rejects the trajectory of the type II tRNALeu V arm.

The trajectory set point of the type II V arm is given by the number of unpaired bases separating the 3’-V arm stem and the Levitt base pair (blue asterisks).

The rule in Archaea is two if by Leu and one if by Ser (as in the Longfellow poem about Paul Revere’s ride).

Type I tRNA V loops and type II V arms are misaligned in tRNA databases. These alignments must be fixed.

Chemical Evolution of Life on Earth

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