Oxygen affinity and amino acid sequence of myoglobins from endothermic and ectothermic fish.

Published

Journal Article

Myoglobin (Mb) buffers intracellular O2 and facilitates diffusion of O2 through the cell. These functions of Mb will be most effective when intracellular PO2 is near the partial pressure of oxygen at which Mb is half saturated (P50) of the molecule. We test the hypothesis that Mb oxygen affinity has evolved such that it is conserved when adjusted for body temperature among closely related animals. We measure oxygen P50s tonometrically and oxygen dissociation rate constants with stopped flow and generate amino acid sequence from cDNA of Mbs from fish with different body temperatures. P50s for the endothermic bluefin tuna, skipjack tuna, and blue marlin at 20 degrees C were 0.62 +/- 0.02, 0.59 +/- 0.01, 0.58 +/- 0.04 mmHg, respectively, and were significantly lower than those for ectothermic bonito (1.03 +/- 0.07 mmHg) and mackerel (1.39 +/- 0.03 mmHg). Because the oxygen affinity of Mb decreases with increasing temperature, the above differences in oxygen affinity between endothermic and ectothermic fish are reduced when adjusted for the in vivo muscle temperature of the animal. Oxygen dissociation rate constants at 20 degrees C for the endothermic species ranged from 34.1 to 49.3 s(-1), whereas those for mackerel and bonito were 102 and 62 s(-1), respectively. Correlated with the low oxygen affinity and fast dissociation kinetics of mackerel Mb is a substitution of alanine for proline that would likely result in a more flexible mackerel protein.

Full Text

Duke Authors

Cited Authors

  • Marcinek, DJ; Bonaventura, J; Wittenberg, JB; Block, BA

Published Date

  • April 2001

Published In

Volume / Issue

  • 280 / 4

Start / End Page

  • R1123 - R1133

PubMed ID

  • 11247835

Pubmed Central ID

  • 11247835

Electronic International Standard Serial Number (EISSN)

  • 1522-1490

International Standard Serial Number (ISSN)

  • 0363-6119

Digital Object Identifier (DOI)

  • 10.1152/ajpregu.2001.280.4.r1123

Language

  • eng