A Chlamydomonas Outer Arm Dynein Mutant with a Truncated Heavy Chain
نویسندگان
چکیده
A new allele of the Chlamydomonas oda4 flagellar mutant (oda4-s7) possessing abnormal outer dynein arms was isolated. Unlike the previously described oda4 axoneme lacking all three (a, /3, and 3") outer-arm dynein heavy chains, the oda4-s7 axoneme contains the c~ and 3' heavy chains and a novel peptide with a molecular mass of •160 kD. The peptide reacts with a mAb (18~B) that recognizes an epitope on the NH2-terminal part of the/3 heavy chain. These observations indicate that this mutant has a truncated ~3 heavy chain, and that the NH2-terminal part of the/3 heavy chain is important for the stable assembly of the outer arms. In averaged electron microscopic images of outer arms from cross sections of axonemes, the mutant outer arm lacks its mid-portion, producing a forked appearance. Together with our previous finding that the mutant odal I lacks the t~ heavy chain and the outermost portion of the arm (Sakakibara, H., D. R. Mitchell, and R. Kamiya. 1991. J. Cell Biol. 113:615-622), this result defines the approximate locations of the three outer arm heavy chains in the axonemal cross section. The swimming velocity of oda4-s7 is 65 + 8/~m/s, close to that of oda4 which lacks the entire outer arm (62 + 8/zm/s) but significantly lower than the velocities of wild type (194 + 23/zm/s) and odal l (119 + 17 #m/s). Thus, the lack of the/3 heavy chain impairs outer-arm function more seriously than does the lack of the ot heavy chain, suggesting that the ot and/3 heavy chains play different roles in outer arm
منابع مشابه
A Chlamydomonas outer arm dynein mutant with a truncated beta heavy chain
A new allele of the Chlamydomonas oda4 flagellar mutant (oda4-s7) possessing abnormal outer dynein arms was isolated. Unlike the previously described oda4 axoneme lacking all three (alpha, beta, and gamma) outer-arm dynein heavy chains, the oda4-s7 axoneme contains the alpha and gamma heavy chains and a novel peptide with a molecular mass of approximately 160 kD. The peptide reacts with a mAb (...
متن کاملPartially functional outer-arm dynein in a novel Chlamydomonas mutant expressing a truncated gamma heavy chain.
The outer dynein arm of Chlamydomonas flagella contains three heavy chains (alpha, beta, and gamma), each of which exhibits motor activity. How they assemble and cooperate is of considerable interest. Here we report the isolation of a novel mutant, oda2-t, whose gamma heavy chain is truncated at about 30% of the sequence. While the previously isolated gamma chain mutant oda2 lacks the entire ou...
متن کاملA Chlamydomonas outer arm dynein mutant missing the alpha heavy chain
A novel Chlamydomonas flagellar mutant (oda-11) missing the alpha heavy chain of outer arm dynein but retaining the beta and gamma heavy chains was isolated. Restriction fragment length polymorphism analysis with an alpha heavy chain locus genomic probe indicated that the oda-11 mutation was genetically linked with the structural gene of the alpha heavy chain. In cross-section electron microgra...
متن کاملA Chlamydomonas Outer Arm Dynein Mutant Missing the te Heavy Chain
A novel Chlamydomonas flagellar mutant (oda-11) missing the ot heavy chain of outer arm dynein but retaining the/3 and 3~ heavy chains was isolated. Restriction fragment length polymorphism analysis with an ct heavy chain locus genomic probe indicated that the oda-11 mutation was genetically linked with the structural gene of the tx heavy chain. In crosssection electron micrographs, the oda-ll ...
متن کامل