The Myofibrillar Protein, Projectin, is Highly Conserved Across Insect Evolution Except for Its PEVK Domain

Abstract

All striated muscles respond to stretch by a delayed increase in tension. This physiological response known as stretch-activation is, however, predominately found in vertebrate cardiac muscle and insect asynchronous flight muscles. Stretch-activation relies on an elastic third filament system composed of giant proteins known as titin in vertebrates or kettin and projectin in insects. The projectin insect protein functions jointly as a 'scaffold and ruler' system during myofibril assembly, and as an elastic protein during stretch activation. An evolutionary analysis of the projectin molecule could potentially provide insight into how distinct protein regions may have evolved in response to different evolutionary constraints. We mined candidate genes in representative insect species from Hemiptera to Diptera, from published and novel genome sequence data and carried out a detailed molecular and phylogenetic analysis. The general domain organization of projectin is highly conserved, as are the protein sequences of its two repeated regions-the Immunoglobulin type C and Fibronectin type III domains. The conservation in structure and sequence is consistent with the proposed function of projectin as a scaffold and ruler. In contrast, the amino acid sequences of the elastic PEVK domains are noticeably divergent although their length and overall unusual amino acid makeup are conserved. These patterns suggest that the PEVK region working as an unstructured domain can still maintain its dynamic, and even its three-dimensional properties, without the need for strict amino acid conservation. Phylogenetic analysis of the projectin proteins also supports a reclassification of the Hymenoptera in relation to Diptera and Coleoptera

Expression of cytoskeletal and molt-related genes is temporally scheduled in the hypodermis of the crayfish Procambarus clarkii during premolt

“…However, the lack of cytoskeleton-related activity may come from a lack of research activity. Titin (designated also projectin, connectin or twitchin) is a long protein which binds to filamentous actin and provides elasticity to muscles, and at the present time it is assigned a function only in the muscular context (Ayme-Southgate et al, 2008). By contrast, the modulatory genes of the actin system were studied in both the cytoskeletal and the muscular contexts.…”

Different transcription regulation routes are exerted by L- and D-amino acid enantiomers of peptide hormones

“…Projectin is a long protein that binds filamentous actin and provides elasticity to muscles, and at present, it is assigned a function only in the muscular context (Ayme-Southgate et al, 2008). The modulatory genes of the actin system were studied in both the cytoskeletal and the muscular contexts.…”

Long indels are disordered: A study of disorder and indels in homologous eukaryotic proteins

“…Certainly, for a few cases, the protein family in question is evolving rapidly while the disordered region remains conserved [31,32]. To examine such examples in our dataset, we compared the evolutionary events within the disordered and ordered regions of all proteins pairs, both with regard to the number of indels in these regions and, additionally, sequence identity, see Figure 6.…”