The alternative sigma factor ppt to helpful the students for learn and acquired the knowledge about that

1. ALTERNATIVE SIGMA
FACTOR
PRESENTED BY
DASTHAGIRI PASHA S
(SPECIFICITY FACTOR)

2. CONTENT
1. MEANING OF SIGMA FACTOR
2. STRUCTURE OF SIGMA FACTOR
3. DIFFERENT TYPES OF SIGMA FACTOR AND
THEIR FUNCTION
4. GROUPS OF SIGMA FACTOR
5. CLASSIFICATION OF SIGMA FACTOR
6. HEAT SHOCK RESPONSE
7. STRESS RESPONSE
8. CONCLUSION

3. MEANING OF SIGMA FACTOR
● Sigma factor are multi- domain subunit of
bacteria in RNA polymerase enzyme.
● These sigma factor recognise particular
promoter region
● RNAP responsible for transcriptional process
from RNA to DNA
● Core enzyme bind and convert into
holoenzyme
● Core enzyme is responsible for chain
elongation

5. STRUCTURE OF SIGMA FACTOR
● The structure of sigma factor has consider the two
terminal regions, one is N terminal and another is
C terminal.
● Sigma factor has been 4 domains sigma 1,sigma
2,sigma 3,and sigma 4 are the conserved domains
of sigma factor.
● Domains of sigma 1- sigma 3 are each interact with
specific promoter elements of RNAP.
● Alternative sigma factor differ from the group one
sigma factor by the complete absense of sigma 1.1

7. DIFFERENT TYPES OF SIGMA FACTOR
AND THEIR FUNCTIONS

9. GROUPS OF SIGMA FACTOR
● In the alternative sigma factor is
classified into two structurally
unrelated families they are…
● Sigma 70
● Sigma 54

11. SIGMA -70

12. Sigma 70 family -
The primary sigma factor of e. coli has a
molecular mass of approximately 70kDa and
designated sigma 70.
Alternative sigma factor within the sigma 70
family are further categorized by the
physiological process they control.
Eg: Stress response

13. SIGMA 54

14. Sigma 54
● An alternative sigma factor that control
nitrogen regulated genes is 54 kDa and
designated sigma 54.
● The sigma 54 family is also widely
represented in many different bacteria and
controls in many different bacteria and
controls a variety of function including
nitrogen metabolism, degradative enzyme
synthesis and flagellar genes.

15. GROUP 1 SIGMA FACTOR
● Group 1 sigma factor is completely absense
of sigma 1.1 the variable presence of sigma 3
promoter specificity
● Group 1 consists of the essentially primary
sigma factor
● Each sigma factor is closely related to sigma
70 of e. coli
● Group 1 sigma factor consist of different
physiological and developmental
characteristics.

16. GROUP 2 SIGMA FACTOR
● Group 2 sigma factor is structurally closely related
to group 1 but lack of sigma 1.1
● Group 2 sigma S usually involved in adaptation to
stress including nutrient limitation and other
stress associated with stationary phase
● In abroad range of stress including high
teperature, light regulation and sugar metabolism
● Group 2 sigma is e. coli sigma S that is responsible
for the general stress response and to induced in
move response to a variety of environment stress.

17. GROUP 3 SIGMA FACTOR
● This group is structurally and functionally diverse,
but usually contain sigma 2 sigma 3 , sigma 4
domains
● They fall into at least 4 phylogenetically distinct
subgroup that patially correlate with function :
flagellum biosynthesis, heat shock response, general
stress and sporulation
● The expression of inverted late genes involved in
flagellum biosynthesis is controlled by sigma factor
closelyrelated e. coli sigma 28 in all motile gram
negative and gram positive bacteria making this the
most widely distributed alternative sigma factor

18. GROUP 4 SIGMA FACTOR
● Group 4 sigma factor is also known as extra
cytoplasmic function group of the frequent role
of member in sensing and responding to signal
that are generated outside of the cell or in the
cell membrane
● Biological roles include envelope stress
response, oxidative stress and general stress
response
● The number of ECT sigma factor encoded by a
genome can vary enormously from zero in
obligate intracellular bacteria.

19. HEAT SHOCK RESPONSE -

21. ● The heat shock response is mechanism of
cellular protection against sudden adverse
environmental growth condition and result in
the production of various heat shock protien .
● Transcriptional regulation of heat shock genes
can be under either positive or negative
control mediated by dedicated regulatory
protiens.
● Some heat shock protiens are also required
during normal growth condition and they are
abundant under all metabolic conditions.

22. STRESS RESPONSE
● Survival under these extreme and rapidly changing
conditions require timely and appropriate alteration in
gene expression and protien activity that occur in a
bacterial cell in response to stimuli signaling these new
environmental conditions.
● The general stress responsive alternative sigma factor
S(rpoS) and B transcribe genes Contributing to bacterial
survival under condition of environmental stress in gram -
negative and in gram -positive bacteria, respectively.
● Solmonella also play a key role in protecting e. coli and s.
enterica from different environmental stress condition,
including starvation, hyperosmolarity, oxidative damage
and reduced PH.

24. CONCLUSION --
● Sigma factor are remarkable protiens that
play both mechanistic and regulatory roles
in transcription.
● One future challenge is therefore to
understand how the structural divergence
of alternative factor translates to functional
difference.
● Biological importance of cross talk between
-based signaling pathway and how bacteria
manage to insulate transcription response
when many factors are presente.

25. REFERENCES
● Alternativesigmafactorresearchgate. Com.
● Www.mdpi.com/journals/biomolecules.