Computational Biology an der LMU München

When two structures or sequences share more similarity than would be expected by chance

Homologous sequences originating from the same ancestor and likely exhibiting the same function

GenInfo Identifier. A GI number is a simple series of digits that are assigned consecutively to each sequence record processed by NCBI. The GI number bears no resemblance to the Version number of the sequence record. Each time a sequence record is changed, it is assigned a new GI number.

for distantly related proteins by virtue of low gap penalty in the algorithm

E-value or expect value is a parameter that describes the number of hits one can "expect" to see by chance when searching in a database of a particular size. The lower the E-value, or the closer it is to zero, the more "significant" the match is 

It decreases exponentially as the S of the match increases.

In a database of the current size one might expect to see 1 match with a similar score simply by chance.

Because the calculation of the E value takes into account the length of the query sequence. These high E values make sense because shorter sequences have a higher probability of occurring in the database purely by chance.

The smaller the database the lower the chance is to find an identical sequence in it. So, smaller databases give you a lower e-value. When a database is larger, it is easier to find an identical sequence, so the E-value will be higher. The lower e-value in a big database is more significant.

- :gap

[gap] : mismatch

+: mismatch but with similar chemical properties

Protparam (ExPaSy)

Interpro