SecA: the ubiquitous component of preprotein translocase in prokaryotes

Schmidt, Michael G.; Kiser, Kevin B.

doi:10.1016/s1286-4579(99)80517-6

Cited by 24 publications

(17 citation statements)

References 115 publications

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“…In other bacteria in which SecA has been studied, SecA is essential and encoded by a single-copy gene (17,34,43). One explanation for the presence of two secA genes in mycobacteria is that they encode redundant functions.…”

Section: Resultsmentioning

confidence: 99%

“…It is an ATPase that provides energy for protein translocation. In addition, SecA binds to nearly all of the components of the Sec pathway, including precursor proteins, chaperones such as SecB, acidic phospholipids in the membrane, and integral membrane components of the translocase (15,33,43). Through cycles of ATP binding and hydrolysis, SecA delivers bound precursor proteins to the translocase and undergoes cycles of membrane insertion and deinsertion that lead to stepwise export of the protein (18,42,50).…”

mentioning

confidence: 99%

“…Additional proteins, SecG and the complex of SecD, SecF, and YajC, are not essential to Sec-dependent export but serve to increase the overall efficiency of the process (14). The Secdependent export pathway is highly conserved among different bacteria (39,43).…”

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confidence: 99%

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Two Nonredundant SecA Homologues Function in Mycobacteria

et al. 2001

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The proper extracytoplasmic localization of proteins is an important aspect of mycobacterial physiology and the pathogenesis of Mycobacterium tuberculosis. The protein export systems of mycobacteria have remained unexplored. The Sec-dependent protein export pathway has been well characterized in Escherichia coli and is responsible for transport across the cytoplasmic membrane of proteins containing signal sequences at their amino termini. SecA is a central component of this pathway, and it is highly conserved throughout bacteria. Here we report on an unusual property of mycobacterial protein export-the presence of two homologues of SecA (SecA1 and SecA2). Using an allelic-exchange strategy in Mycobacterium smegmatis, we demonstrate that secA1 is an essential gene. In contrast, secA2 can be deleted and is the first example of a nonessential secA homologue. The essential nature of secA1, which is consistent with the conserved Sec pathway, leads us to believe that secA1 represents the equivalent of E. coli secA. The results of a phenotypic analysis of a ⌬secA2 mutant of M. smegmatis are presented here and also indicate a role for SecA2 in protein export. Based on our study, it appears that SecA2 can assist SecA1 in the export of some proteins via the Sec pathway. However, SecA2 is not the functional equivalent of SecA1. This finding, in combination with the fact that SecA2 is highly conserved throughout mycobacteria, suggests a second role for SecA2. The possibility exists that another role for SecA2 is to export a specific subset of proteins.

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

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Two Nonredundant SecA Homologues Function in Mycobacteria

et al. 2001

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“…The SecA1 protein is an essential component of the preprotein translocase ATPase that provides the driving force for the export of proteins across the bacterial cytoplasmic membrane (9). It has recently been shown that sufficient variability exists in the sequence of the secA1 gene of mycobacteria to allow discrimination of 29 species (13).…”

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confidence: 99%

Analysis of secA1 Gene Sequences for Identification of Nocardia Species

2006

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Molecular methodologies, especially 16S rRNA gene sequence analysis, have allowed the recognition of many new species of Nocardia and to date have been the most precise methods for identifying isolates reliably to the species level. We describe here a novel method for identifying Nocardia isolates by using sequence analysis of a portion of the secA1 gene. A region of the secA1 gene of 30 type or reference strains of Nocardia species was amplified using secA1-specific primers. Sequence analysis of 468 bp allowed clear differentiation of all species, with a range of interspecies similarity of 85.0% to 98.7%. Corresponding 16S rRNA gene sequences of a 1,285-bp region for the same isolates showed a range of interspecies similarity of 94.4 to 99.8%. In addition to the type and reference strains, a 468-bp fragment of the secA1 gene was sequenced from 40 clinical isolates of 12 Nocardia species previously identified by 16S rRNA gene sequence analysis. The secA1 gene sequences of most isolates showed >99.0% similarity to the secA1 sequences of the type or reference strain to which their identification corresponded, with a range of 95.3 to 100%. Comparison of the deduced 156 amino acid sequences of the SecA1 proteins of the clinical isolates showed between zero and two amino acid residue differences compared to that of the corresponding type or reference strain. Sequencing of the secA1 gene, and using deduced amino acid sequences of the SecA1 protein, may provide a more discriminative and precise method for the identification of Nocardia isolates than 16S rRNA gene sequencing.

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“…The SecA protein is found in all sequenced bacterial genomes and is involved in the export of proteins to the periplasmic compartment (Valentin, 1997;Schmidt & Kiser, 1999). In this protein, we have identified a 2 aa insert in a highly conserved region that is specific to cyanobacteria (Fig.…”

Section: Resultsmentioning

confidence: 99%

Molecular signatures in protein sequences that are characteristic of cyanobacteria and plastid homologues

Gupta

Pereira

Chandrasekera

et al. 2003

INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLO

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Fourteen conserved indels (i.e. inserts or deletions) have been identified in 10 widely distributed proteins that appear to be characteristic of cyanobacterial species and are not found in any other group of bacteria. These signatures include three inserts of 6, 7 and 28 aa in the DNA helicase II (UvrD) protein, an 18-21 aa insert in DNA polymerase I, a 14 aa insert in the enzyme ADP-glucose pyrophosphorylase, a 3 aa insert in the FtsH protein, an 11-13 aa insert in phytoene synthase, a 5 aa insert in elongation factor-Tu, two deletions of 2 and 7 aa in ribosomal S1 protein, a 2 aa insert in the SecA protein, a 1 aa deletion and a 6 aa insert in the enzyme inosine-59-monophosphate dehydrogenase and a 1 aa deletion in the major sigma factor. These signatures, which are flanked by conserved regions, provide molecular markers for distinguishing cyanobacterial taxa from all other bacteria and they should prove helpful in the identification of cyanobacterial species, simply on the basis of the presence or absence of these markers in the corresponding proteins. The signatures in six of these proteins (SecA, elongation factor-Tu, ADP-glucose pyrophosphorylase, phytoene synthase, FtsH and ribosomal S1 protein) are also commonly present in plastid homologues from plants and algae (chlorophytes, chromophytes and rhodophytes), indicating their specific relationship to cyanobacteria and supporting their endosymbiotic origin from these bacteria. In phylogenetic trees based on a number of these proteins (SecA, UvrD, DNA polymerase I, elongation factor-Tu) that were investigated, the available cyanobacterial homologues grouped together with high affinity (>95 % bootstrap value), supporting the view that the cyanobacterial phylum is monophyletic and that the identified signatures were introduced in a common ancestor of this group.

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SecA: the ubiquitous component of preprotein translocase in prokaryotes

Cited by 24 publications

References 115 publications

Two Nonredundant SecA Homologues Function in Mycobacteria

Two Nonredundant SecA Homologues Function in Mycobacteria

Analysis of secA1 Gene Sequences for Identification of Nocardia Species

Molecular signatures in protein sequences that are characteristic of cyanobacteria and plastid homologues

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