some proteins (such as HBB) can vary quite a bit from species to species. others (ex., tubulin) vary little from species to species? Why?
Proteins are fundamental biological molecules that perform a wide range of functions in living organisms. Their sequences are encoded in genes, and variations in protein sequences can arise due to evolutionary processes. The degree of variation in protein sequences among different species can depend on several factors, such as the protein's function, conservation, and evolutionary constraints.
Some proteins, like HBB (Hemoglobin Beta), show significant variation across species. HBB is responsible for transporting oxygen in red blood cells and has evolved in response to the unique physiological needs of different organisms. The variations in HBB sequence result from the selective pressures imposed by environmental conditions, such as oxygen availability and temperature. Since different species inhabit diverse environments, variations in HBB sequences allow them to adapt and optimize their oxygen transport abilities accordingly.
Conversely, proteins like tubulin exhibit little variation between species. Tubulin is an essential protein involved in the formation of microtubules, which play crucial roles in cell division, intracellular transport, and structural support. The conservation of tubulin sequences across species is primarily attributed to its essential function and structural integrity, which are conserved throughout evolution. Any significant alterations in tubulin's amino acid sequence could potentially disrupt its structural stability or impair its function. Therefore, evolutionary constraints prevent widespread variations in tubulin sequences to maintain its essential role in cells.
To determine the extent of variation for a particular protein across species, researchers typically compare the protein sequences of different organisms. This can be done by utilizing specialized databases, such as the UniProt database, which provides comprehensive information about protein sequences and their variations across various species. Comparing protein sequences allows scientists to study the molecular evolution of proteins and understand the factors influencing their variability.
In summary, the extent of protein variation across species is influenced by factors like their function, evolutionary constraints, and selective pressures. Proteins that have crucial roles within organisms and are structurally important tend to exhibit limited variations, while those involved in specialized functions and subjected to diverse selective pressures can display significant variation. Exploring protein databases and performing comparative sequence analyses can help researchers investigate the variations and understand the evolutionary processes behind them.