Experimental dissection of flagellar surface motility in chlamydomonas

Experiments have explored the possible relationships between the flagellar surface motility of chlamydomonas, visualized as translocation of polystyrene beads by paralyzed (pf) mutants (Bloodgood, 1977, J. Cell Biol. 15:983-989), and the capacity of gametic flagella to participate in the mating reaction. While vegetative and gametic flagella bind beads with equal efficiencies and are capable of transporting them along entire flagellar lengths, beads on vegetative flagella are primarily associated with the proximal half of the flagella whereas those of gametic flagella exhibit no such preference. This difference may relate to the "tipping" response of gametes during sexual flagellar agglutination (Goodenough and Jurivich, 1978, J. Cell Biol. 79:680-693). Colchicine, vinblastine, chymotrypsin, cytochalasins B and D, and anti-β-tubulin antiserum are all able to inhibit the binding of beads to the flagellar suface. Trysin digestion and an antiserum directed against whole chlamydomonas flagella have no effect on the ability of flagella to bind beads, but the beads remain immobile. These results suggest that at least two flagellar activities participate in surface motility: (a) bead binding, which may involve a tubulin-like component at the flagellar surface; and (b) bead translocation, which may depend on a second component (e.g. an ATPase) of the flagellar surface. Surface motility is shown to be distinct from gametic adhesiveness per se, but it may participate in concentrating dispersed agglutinins, in driving them toward the flagellar tips, and/or in generating a signal-to-fuse from the flagellar tips to the cell body. Directly supporting these concepts is the observation that bound beads remain immobilized at the flagellar tips during the "tip-locking" stage of pf x pf matings, and the observation that bound ligands such as antibody fail to be tipped by trypsinized flagella.     

In-frame single codon deletion in the Mmalton deficiency allele of alpha 1-antitrypsin.

A deficiency of the plasma protease inhibitor alpha 1-antitrypsin (alpha 1AT) is usually a consequence of the PI*Z allele. Mmalton is another deficiency allele which, like Z alpha 1AT, is associated with hepatocyte inclusions and impaired secretion. We report here the sequence of the PI Mmalton allele, which contains a 3-bp deletion coding for one of two adjacent phenylalanine residues (amino acid 51 or 52 of the mature protein). Using oligonucleotide hybridization of polymerase chain reaction-amplified DNA, we have demonstrated cosegregation of the PI Mmalton protein and the 3-bp deletion in the family in which this allele was originally described and in three other, unrelated kindreds. This deletion is found exclusively in PI Mmalton alleles and not in the normal M2 alleles from which, to judge on the basis of haplotype data, the Mmalton mutation must have been derived. In polyacrylamide isoelectric focusing (PIEF) gels, the isoelectric point of Mmalton is only slightly more cathodal than M2, a finding consistent with the loss of a single uncharged amino acid. To judge on the basis of X-ray crystallography data for the normal alpha 1AT protein, the deletion of aa 51/52 would shorten one strand of the beta sheet, B6, apparently preventing normal processing and secretion.