temperature 5: cardiac proteins, heart function, and high temperatures

Question 1

Ca+ sensitivity of myofilament force generation allowed…

Answer 1

the evolution of endothermy

• vetebrates are evolving towards myofilaments less sensitive to Ca2+
• this allows cardiac myofilaments to operate at higher temperatures, as sensitivity to Ca2+ increases with increasing temp

Question 2

how has troponin complex evolved during evolution of endothermy?

Answer 2

-reduced sensitivity to Ca2+ at Ca binding sites of site 2 force a greater amount of Ca needed to activate force generators, allowing mammals to operate at higher temperature

Question 3

what prevents the heart from getting stuck in contraction?

Answer 3

.

Question 4

mammalian vs salmonid troponin C sequence; operative sequences?

Answer 4

d, vlg; altering mammal troponin increased Ca2+ affinity to similar levels as salmonid due to increased Ca binding to site 2

Question 5

does troponin 1 also play a role in reduction in Ca sensitivity of vertebrate heart?

Answer 5

• yes; change in sequence of cTnl is critical for allowing contractions at higher temperatures

Question 6

appearence of Asp at 2 in cTnC

Answer 6

-vertebra branch

Question 7

appearance of Leu and Gly at 29 and 30 of TnC

Answer 7

-amniote branch

Question 8

appearance of Ala at 163 in cTnl

Answer 8

-mammalian branch (post-monotremes)

Question 9

summary

Answer 9

• changes to cTnC and cTnl are vital to enabling cardiac function at high temperatures of 37C
• use of comparative approach provides significant insight into functions relationships