provided by Dr. Karlheinz Altendorf (Universitait Osnabriick, Osnabriick, Germany).

Mouse monoclonal antibodies against the peptide epitope of hemagglutinin protein of

human influenza virus (HA epitope tag) were purchased from Roche Molecular

Biochemicals (Indianapolis, IN). Monoclonal antibodies against the epitope found in the

P and V proteins of the paramyxovirus, SV5 (V5 epitope tag) were purchased from

Invitrogen .

Strains and Media

 The bacterial strains used to create the epitope tagged b subunits include the wild

type b subunit expression plasmid, pKAM14, and plasmids used to express b subunits

shortened or lengthened by 7 amino acids, pAUL3 and pAUL19, respectively, and have

been described previously (193, 194, 203). The plasmids encoding the different uncF(b)

genes were used to compliment E. coli strain KM2 (Ab) carrying a chromosomal deletion

of the gene (218). All strains were streaked onto plates containing Minimal A media

supplemented with succinate (0.2% w/v), to determine enzyme viability. Cells harvested

for membrane preparation were grown in Luria Bertani media supplemented with glucose

(0.2% w/v) (LBG). Isopropyl-1 -thio-P-D-galactopyranoside (IPTG)(40 Clg/ml),

ampicillin (Ap) (100Clg/ml), and chloramphenicol (Cm) (25 Clg/ml) were added to media

as needed. All cultures were incubated at 37oC for the appropriate duration.

Recombinant DNA Techniques

 Plasmid purification. Plasmid DNA was purified with the Qiagen Mini-Prep and

Maxi-Prep kits according to the protocols provided from the manufacturer. Mini-preps

required 4 mL (high copy plasmid) or 6 mL (low copy plasmid) of an overnight bacterial

culture carrying the desired plasmid. Maxi-preps required a 500 mL culture grown