The Science of Existence (122-10-1) Actin


Closely related protein isoforms can exhibit functional differences. ~ Russian biochemist Anna Kashina et al

Actin is a family of proteins essential to cell functioning. Actin is found in all eukaryotic cells except roundworm sperm. Actin has equivalent cousins (homologs) in prokaryotes.

Distinct actin variants – isoforms – perform a wide variety of different roles, including maintaining cell shape, cell motility, cell division, cell signaling, and intercellular communication. These isoforms are created by mRNA selecting specific exons or through post-translation modifications.

Humans have 6 actin isoforms. 2 in particular – β-actin and γ-actin – are nearly identical in their structure. (β-actin and γ-actin exhibit only minor differences in 4 amino acids in just 1 region of these proteins. Actin altogether comprises 376 amino acids, folded into a labyrinthian arrangement that defines the functional potentialities of this protein family.) Yet these near-twin proteins carry out distinct roles. In mammals, β-actin is critical to embryogenesis, whereas γ-actin plays a regulatory role in managing the proteins in a cell’s cytoskeleton.

Via epigenetic activity, a single gene can produce multiple proteins. Very minor physical changes can have a profound impact on proteome diversity and the behaviors of proteins.

Conversely, different genes may encode selfsame bioproducts. Despite being nearly identical proteins, β-actin and γ-actin are encoded by separate genes. (6 actin genes are expressed in birds and mammals.) The epigenetic activities in producing β-actin and γ-actin are significantly dissimilar yet yield physical self-similarity.

The parts of genes that we think of as being silent actually encode very key functional information. ~ Anna Kashina

Actin illustrates how labyrinthine genetics is, but also shows that there is an energetic component essential to life at the molecular level. The study of genetics has been confined to physical artifacts – DNA sequences – and associated processes upon those artifacts. Neither genetics nor biochemistry can explain how a slight physical difference in proteins affords very distinct behavioral profiles, as with β-actin and γ-actin. More generally, these sciences have no explanation for how DNA sequences can encode the divergent behavioral paradigms which proteins exhibit. (Geneticists cannot even explain how genes encode the patterns of folding which practically define the behavioral potentialities of proteins.) Knowing about epigenetic tweaks does not demystify how protein personalities exist.

Matter transformations cannot explain coherent energy patterns. The issue becomes completely perplexing when considering how molecules such as proteins can behave intelligently through their production via genetics: how matter can inform knowledge and decision-making ability, which are clearly traits of a mind, not a molecular body.