Table 1.

Summary of 704 ORFs responsive to the loss of SRP

Category	No. of ORFs	No. induced	No. repressed	% of total
Chaperone/heat shock	31	30	1	4.4
Protein synthesis	77	1	76	11
Mitochondrial/energy generationa	36	1	35	5
Metabolismb	97	29	68	14
Transcription	18	7	11	2.5
RNA processing	6	5	1	0.8
DNA replication, recombination, repair, structure	18	3	15	2.5
Protein modification	11	1	10	1.6
Protein degradation	7	5	2	1
Vesicular transport	11	4	7	1.6
Signaling	7	1	6	1
Cell wall/structural	12	2	10	1.7
Mating/budding	4	0	4	0.6
Cell cycle	4	2	2	0.6
Other	5	1	4	0.7
Uncharacterized ORFs	360	148	212	51
Total	704	240	464	100%

^a Twenty-three small molecule transporters, 74 involved in the metabolism of amino acids (20), carbohydrates (17), nucleotides (15), lipids/fatty acids (17), phosphate (2), and others (3). 

^b Cells disrupted for SRP function rapidly lose the ability to grow on nonfermentable carbon sources, i.e., unless selective pressure is applied to the contrary, they become rho⁻. The reason for this tendency is unknown; it is not a prerequisite for survival as cells can be forced to retain mitochondrial function if they are continuously grown on nonfermentable carbon sources. We previously characterized protein translocation defects of rho⁻ strains following SRP-depletion and found that these strains can also adapt (Ogg et al., 1992). We therefore conclude that a loss of respiratory function is not responsible for adaptation.