PROSITE documentation PDOC00293
Hemolysin-type calcium-binding region signature


Gram-negative bacteria produce a number of proteins which are secreted into the growth medium by a mechanism that does not require a cleaved N-terminal signal sequence. These proteins, while having different functions, seem [1] to share two properties: they bind calcium and they contain a variable number of tandem repeats consisting of a nine amino acid motif rich in glycine, aspartic acid and asparagine. It has been shown [2] that such a domain is involved in the binding of calcium ions in a parallel β roll structure. The proteins which are currently known to belong to this category are:

  • Hemolysins from various species of bacteria. Bacterial hemolysins are exotoxins that attack blood cell membranes and cause cell rupture. The hemolysins which are known to contain such a domain are those from: E. coli (gene hlyA), A. pleuropneumoniae (gene appA), A. actinomycetemcomitans and P. haemolytica (leukotoxin) (gene lktA).
  • Cyclolysin from Bordetella pertussis (gene cyaA). A multifunctional protein which is both an adenylate cyclase and a hemolysin.
  • Extracellular zinc proteases: serralysin (EC from Serratia, prtB and prtC from Erwinia chrysanthemi and aprA from Pseudomonas aeruginosa.
  • Nodulation protein nodO from Rhizobium leguminosarum.

We derived a signature pattern from conserved positions in the sequence of the calcium-binding domain.


This pattern is found once in nodO and the extracellular proteases but up to 5 times in some hemolysin/cyclolysins.

Last update:

October 1993 / Text revised.


Technical section

PROSITE method (with tools and information) covered by this documentation:

HEMOLYSIN_CALCIUM, PS00330; Hemolysin-type calcium-binding region signature  (PATTERN)


1AuthorsEconomou A. Hamilton W.D.O. Johnston A.W. Downie J.A.
TitleThe Rhizobium nodulation gene nodO encodes a Ca2(+)-binding protein that is exported without N-terminal cleavage and is homologous to haemolysin and related proteins.
SourceEMBO J. 9:349-354(1990).
PubMed ID2303029

2AuthorsBaumann U. Wu S. Flaherty K.M. McKay D.B.
TitleThree-dimensional structure of the alkaline protease of Pseudomonas aeruginosa: a two-domain protein with a calcium binding parallel beta roll motif.
SourceEMBO J. 12:3357-3364(1993).
PubMed ID8253063

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