Divergent neural beta tubulin from the Antarctic fish Notothenia coriiceps neglecta: potential sequence contributions to cold adaptation of microtubule assembly.
The cytoplasmic microtubules of the cold-adapted Antarctic fishes, unlike those of homeotherms and temperate poikilotherms, assemble and function at body temperatures in the range -1.8 to +2 degrees C. To determine whether alterations to the primary sequence of beta tubulin may contribute to enhancement of microtubule assembly at cold temperatures, we have cloned and sequenced a 1.8-kilobase neural beta-chain cDNA, Ncn beta 1, from an Antarctic rockcod, Notothenia coriiceps neglecta. Based on nucleotide sequence homology, Ncn beta 1 probably corresponds to a class-II beta-tubulin gene. The 446-residue beta chain encoded by Ncn beta 1 is closely related (sequence homology approximately 95%) both to the neural class-I/II isotypes and to the neural/testicular class-IV variants of higher vertebrates, but the sequence of its carboxy-terminal isotype-defining region (residues 431-446) has diverged markedly (> or = 25% change relative to the I/II/IV referents). Furthermore, the Ncn beta 1 polypeptide contains six unique amino-acid substitutions (five conservative, one nonconservative) not found in other vertebrate brain isotypes, and the carboxy-terminal region possesses a unique tyrosine inserted at position 442. We conclude that Ncn beta 1 encodes a class-II beta tubulin that contains sequence modifications, located largely in its interdimer contact domain, that may contribute to cold adaptation of microtubule assembly.
Detrich
H W
HW
Department of Biology, Northeastern University, Boston, Massachusetts 02115.
Parker
S K
SK
D000064:Acclimatization / Q000235:genetics*; D000595:Amino Acid Sequence; D000818:Animals; D000864:Antarctic Regions; D001483:Base Sequence; D003062:Codon; D003081:Cold Climate; D004247:DNA / Q000235:genetics; D005399:Fishes / Q000235:genetics*; D008870:Microtubules / Q000502:physiology*; D008969:Molecular Sequence Data; D005810:Multigene Family; D014404:Tubulin / Q000235:genetics*
D003062:Codon; D014404:Tubulin; D004247:DNA