TABLE 1.

Sequence analysis of SecA fragments^a

SecA fragment (kDa)	N-terminal sequence
Generated in the presence of membrane
Extracted from membrane
66	14NDRT
48	361EGVQIQNENQ
36	1MLIKLLtKVF
	9vFGSRNDRTL
	14nDRTLRRMRK
31	361EGVQIQNENQ
	575SGRQGdaGS
s29	361EGVQIQNENQ
Recovered from supernatant
66	9VFGSRNDRTL
	14NDRTLRRMRK
36	9VFGSRNDRTL
	14NDRTLRRMRK
s29	361EGVQIQNENQ
Generated in the absence of membrane
In buffer containing ATP and precursor
66	9VFGSRNDRTL
	14NDRTLRRMRK
36	9VFGSRNDRTL
	14NDRTLRRMRK
s29	361EGVQIQNENQ
In buffer with low trypsin
66	9VFGSRNDRTL
50	9VFGsRNDRTL
36	104TGEGKTLTAT
30	644QLLEQQDVA

^aSecA fragments were generated in the presence of membranes as described in Materials and Methods and were subjected to peptide-sequencing analysis. Soluble SecA (1 mg/ml) was digested with trypsin on ice for 15 min in buffer in the presence of energy source and proOmpA (1 mg of trypsin/ml) or in the absence of energy source and proOmpA (20 μg of trypsin/ml). The resulting SecA fragments were then analyzed in the same manner as the SecA fragments generated in the presence of membranes. Identified SecA sequences are shown in single-letter code. Uppercase letters represent amino acids of the analyzed sequences which match the known SecA sequence (31), whereas lowercase letters represent unconfirmed residues.