Extensive Sequence Conservation Among Insect, Nematode, and Vertebrate Vitellogenins Reveals Ancient Common Ancestry

Abstract

The eggs of most oviparous animals are provisioned with a class of protein called vitellogenin (Vg) which is stored as the major component of yolk. Until recently, deduced amino acid sequences were available only from vertebrate and nematode Vgs, which proved to be homologous. The sequences of several insect Vgs are now known, but early attempts at pairwise alignments with vertebrate and nematode Vgs have been problematic, leading to conflicting conclusions about how closely insect Vgs are related to the others. In this paper we demonstrate that insect Vg sequences can be confidently aligned with one another along their entire lengths and with multiple vertebrate and nematode Vg sequences along most of their spans. Although divergence is high, conservation among insect, vertebrate, and nematode Vg sequences is widespread with a preponderance of glycine, proline, and cysteine residues among strictly conserved amino acids, establishing conclusively that Vgs from the three phyla are homologous. Areas of least-certain alignment are primarily in and around insect and vertebrate polyserine domains which are not homologous. Phylogenetic reconstructions of Vgs based on sequence identities indicate that the insect lineage is the most diverged and that the mammalian serum protein, apolipoprotein B-100, arose from a Vg ancestor after the nematode/vertebrate divergence.

Receptor-Ligand Interaction between Vitellogenin Receptor (VtgR) and Vitellogenin (Vtg), Implications on Low Density Lipoprotein Receptor and Apolipoprotein B/E

“…The receptor-ligand pairs of VtgR-Vtg and LDLR/VLDLRapolipoprotein have existed together in fish, amphibians, reptiles, and birds for millions of years (42,43). In the lower species, including insects and nematode, VtgR was the predominant form of receptor.…”

Biochemical and molecular characterization of two cytidine deaminases in the nematode Caenorhabditis elegans

“…For example, the major secretory products of the C. elegans intestine are the vitellogenins, or yolk proteins, that are secreted into the pseudocolem for uptake into the developing oocyte [39,40]. Intriguingly, vitellogenins are distantly related to apoB, and it is generally accepted that apoB arose from a vitellogenin precursor after the nematode\vertebrate divergence [41,42]. Thus the co-localization of the ancestral apoB (vitellogenin) and apobec-1 (CDD) to the intestine of C. elegans might hold clues for understanding the mechanisms by which apoB editing evolved in higher organisms.…”

Vitellogenin isolation, purification and antigenic cross-reactivity in three teleost species

“…Vtg is considered to be an ancient protein for which, in most species studied, the genes belong to multigene families (Chen et al, 1997). Some regions, notably the E 2 receptor binding region, are highly conserved (Bidwell and Carson, 1995).…”