Characterization of human thioredoxin-like 2. A novel microtubule-binding thioredoxin expressed predominantly in the cilia of lung airway epithelium and spermatid manchette and axoneme.
We describe here the cloning and characterization of a novel member of the thioredoxin family, thioredoxin-like protein 2 (Txl-2). The Txl-2 open reading frame codes for a protein of 330 amino acids consisting of two distinct domains: an N-terminal domain typical of thioredoxins and a C-terminal domain belonging to the nucleoside-diphosphate kinase family, separated by a small interface domain. The Txl-2 gene spans approximately 28 kb, is organized into 11 exons, and maps at locus 3q22.3-q23. A splicing variant lacking exon 5 (Delta 5Txl-2) has also been isolated. By quantitative real time PCR we demonstrate that Txl-2 mRNA is ubiquitously expressed, with testis and lung having the highest levels of expression. Unexpectedly, light and electron microscopy analyses show that the protein is associated with microtubular structures such as lung airway epithelium cilia and the manchette and axoneme of spermatids. Using in vitro translated proteins, we demonstrate that full-length Txl-2 weakly associates with microtubules. In contrast, Delta 5Txl-2 specifically binds with very high affinity brain microtubule preparations containing microtubule-binding proteins. Importantly, Delta 5Txl-2 also binds to pure microtubules, proving that it possesses intrinsic microtubule binding capability. Taken together, Delta 5Txl-2 is the first thioredoxin reported to bind microtubules and might therefore be a novel regulator of microtubule physiology.
Sadek
Christine M
CM
Center for Biotechnology, Department of Biosciences at NOVUM, Karolinska Institutet, Huddinge S-14157, Sweden.
Jiménez
Alberto
A
Damdimopoulos
Anastasios E
AE
Kieselbach
Thomas
T
Nord
Magnus
M
Gustafsson
Jan-Ake
JA
Spyrou
Giannis
G
Davis
Elaine C
EC
Oko
Richard
R
van der Hoorn
Frans A
FA
Miranda-Vizuete
Antonio
A
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000502:physiology; D001923:Brain Chemistry; D002352:Carrier Proteins; D002923:Cilia / Q000502:physiology* / Q000648:ultrastructure; D003001:Cloning, Molecular; D017931:DNA Primers; D006801:Humans; D007150:Immunohistochemistry; D008168:Lung / Q000166:cytology / Q000502:physiology* / Q000648:ultrastructure; D008297:Male; D051379:Mice; D016253:Microscopy, Immunoelectron; D008869:Microtubule-Associated Proteins / Q000737:chemistry* / Q000378:metabolism*; D008870:Microtubules / Q000502:physiology*; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D011490:Protein Disulfide Reductase (Glutathione); D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D020545:Respiratory Mucosa / Q000166:cytology / Q000502:physiology*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013087:Spermatids / Q000737:chemistry / Q000502:physiology*; D013879:Thioredoxins / Q000737:chemistry* / Q000378:metabolism*
D002352:Carrier Proteins; D017931:DNA Primers; C404105:GLRX3 protein, human; D008869:Microtubule-Associated Proteins; D011994:Recombinant Proteins; D013879:Thioredoxins; D011490:Protein Disulfide Reductase (Glutathione); C498606:Txnl2 protein, mouse