FIGURE 4.

LOGO alignments of the N-terminal portions of NAGS from 90 mammals (A) and 61 fish, amphibians and reptiles (B). NAGS is present in most vertebrates, but its efficient activity is crucial for survival of land dwelling organisms such as mammals that require highly efficient urea cycle. To examine protein sequence features associated with NAGS specialization in aquatic and land-dwelling vertebrates we compared alignments of NAGS from mammals and fish, amphibians and reptiles. There are three regions with differing degrees of conservation: N-terminal mitochondrial targeting signal, followed by VS, and conserved domain. Mammalian VS has higher proline content and greater sequence conservation than the VS from fish, amphibians and reptiles. Prolines are shown in magenta. Tan, mitochondrial targeting sequence; Yellow/lime green, variable segment (VS); Blue, conserved domain.