Structure and organization of tRNA, rRNA, and protein genes in neurospora crassa mitochondria.

Our studies on Neurospora crassa mitochondria have included sequence analysis of tRNAs, mapping and cloning of the tRNA, rRNA, and protein genes and the DNA sequence analysis of these genes. Results from tRNA sequence analyses explain how the mitochondrial protein synthesizing system can function with a much smaller number of tRNAs than other systems. Mapping studies have shown that the two rRNA genes and almost all of the tRNA genes are clustered onto a third of the mitochondrial genome. The two rRNA genes and all of the tRNA genes are coded for by the same DNA strand. DNA sequence analysis has provided several interesting results. Twenty-four tRNA genes have been identified. Highly conserved GC rich palindromic sequences flank tRNA genes. The intervening sequence within the large rRNA gene has a long open reading frame capable of coding for a protein 426 amino acids long. The gene for cytochrome oxidase subunit 3 has been localized within the tRNA-rRNA gene cluster and has been sequenced. This gene is also flanked by the highly conserved GC rich palindromic DNA sequences.